From 06df4be96f7e180bce8c1c2b8c4fdbe0d746ed84 Mon Sep 17 00:00:00 2001
From: Adrien Jaguenet <adrien@jague.net>
Date: Wed, 16 Sep 2026 22:41:57 +0200
Subject: [PATCH] Artillery + encirclement + budget

---
 AGENTS.md                          |   7 +
 client/css/style.css               |  63 ++-
 client/index.html                  |  13 +-
 client/js/game_screen.js           |  86 ++++-
 client/js/map_view.js              | 166 +++++++-
 client/js/modals.js                |  98 ++++-
 nix/module.nix                     |  43 ++-
 shared/data.js                     |  98 ++++-
 shared/game_state.js               | 597 ++++++++++++++++++++++++++++-
 shared/hex_pathfinder.js           |  12 +-
 shared/rules.js                    |  28 +-
 tests/data_test.js                 |  20 +-
 tests/framework/helpers.js         |   1 +
 tests/game_screen_test.js          |  73 +++-
 tests/game_state_buildings_test.js |  42 +-
 tests/hex_pathfinder_test.js       |  16 +
 tests/modals_test.js               |  54 +++
 tests/rules_test.js                |  58 ++-
 tests/run_tests.js                 |   4 +
 19 files changed, 1398 insertions(+), 81 deletions(-)

diff --git a/AGENTS.md b/AGENTS.md
index 2ad436a..035d753 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -79,3 +79,10 @@ There is no linter, formatter, or CI. Do not invent commands beyond these.
   `/client/index.html` and proxying `/ws` to the local Node server. The browser
   client connects to the page's own origin, so HTTPS gives it `wss://`.
 - Build locally with `nix build .#server` and `nix build .#web`.
+- Updating without a rebuild: set `services.battle-for-tismo.appDirectory` to a
+  writable checkout (e.g. `/opt/battle-for-tismo`); the unit then runs
+  `node <dir>/server/server.js` instead of the Nix-store copy. Serve nginx
+  `client/` and `shared/` from that same checkout (e.g. `alias` locations), then
+  `git pull` and `systemctl restart battle-for-tismo`. Keep the client and
+  server trees on the same commit: the client mirrors the server's movement
+  model, so a mismatched pair makes prediction fight the server.
diff --git a/client/css/style.css b/client/css/style.css
index 13da9fb..ce1f0f9 100644
--- a/client/css/style.css
+++ b/client/css/style.css
@@ -169,12 +169,29 @@ input:focus, select:focus { border-color: var(--accent); }
 
 .entity { position: absolute; }
 .unit {
+  --unit-size: 38px;
   width: 38px;
   height: 38px;
   margin-left: -19px;
   margin-top: -19px;
   cursor: pointer;
 }
+.unit .unit-statuses,
+.city .city-statuses {
+  position: absolute;
+  display: flex;
+  gap: 1px;
+  pointer-events: none;
+  z-index: 2;
+}
+.unit .unit-statuses { top: -4px; right: -4px; }
+.city .city-statuses { top: -6px; left: 50%; transform: translateX(-50%); }
+.status-icon {
+  width: calc(var(--unit-size, 38px) / 5);
+  height: calc(var(--unit-size, 38px) / 5);
+  display: block;
+  filter: drop-shadow(0 0 1px rgba(0, 0, 0, 0.9));
+}
 .unit .body {
   width: 100%;
   height: 100%;
@@ -216,12 +233,19 @@ input:focus, select:focus { border-color: var(--accent); }
   cursor: pointer;
   box-shadow: 0 2px 6px rgba(0, 0, 0, 0.7);
 }
-.city .label {
-  margin-top: 2px;
+/* City names live in their own layer above every unit, marker and status icon,
+   so they stay legible instead of being covered by whatever is nearby. */
+.city-label-layer { pointer-events: none; }
+.city-label {
+  position: absolute;
+  transform: translate(-50%, 0);
+  margin-top: 15px;
   font-size: 11px;
   color: #fff;
+  text-align: center;
   text-shadow: 0 1px 2px #000, 0 0 4px #000;
   white-space: nowrap;
+  pointer-events: none;
 }
 
 .path-seg {
@@ -304,6 +328,30 @@ input:focus, select:focus { border-color: var(--accent); }
 .health-bar { width: 220px; height: 12px; background: rgba(30, 0, 0, 0.8); border-radius: 6px; overflow: hidden; margin-top: 6px; }
 #unit-health-fill { height: 100%; background: linear-gradient(180deg, #6fe08a, #2fa04d); }
 
+.unit-stats { display: flex; gap: 16px; margin-top: 6px; }
+.unit-stat {
+  font-size: 13px;
+  color: var(--muted);
+  border-bottom: 1px dotted rgba(159, 176, 200, 0.5);
+  cursor: help;
+}
+.unit-stat:hover { color: var(--text); }
+
+.tooltip {
+  position: absolute;
+  z-index: 80;
+  max-width: 280px;
+  padding: 6px 10px;
+  border-radius: 7px;
+  background: rgba(8, 12, 20, 0.97);
+  border: 1px solid var(--panel-border);
+  color: var(--text);
+  font-size: 12px;
+  white-space: nowrap;
+  pointer-events: none;
+  box-shadow: 0 6px 18px rgba(0, 0, 0, 0.6);
+}
+
 /* --------------------------------------------------------------- modals -- */
 
 .modal {
@@ -372,6 +420,17 @@ input:focus, select:focus { border-color: var(--accent); }
 .row-card .cost { font-size: 12px; color: var(--muted); margin-top: 3px; }
 .row-card .actions { display: flex; flex-direction: column; gap: 6px; justify-content: center; }
 .row-card .actions .aero { min-width: 170px; }
+.row-card .value {
+  display: flex;
+  align-items: flex-start;
+  justify-content: flex-end;
+  min-width: 140px;
+  font-weight: 600;
+}
+.row-card .value.positive { color: #8fe3a8; }
+.row-card .value.negative { color: #ff9a9a; }
+.row-card .budget-detail { margin-top: 4px; }
+.row-card .budget-line { font-size: 12px; color: var(--muted); margin-top: 2px; }
 
 .training-status { padding: 0 18px 16px; }
 .progress { height: 14px; margin-top: 8px; background: rgba(0, 0, 0, 0.5); border-radius: 7px; overflow: hidden; }
diff --git a/client/index.html b/client/index.html
index f0c7055..a37fbd9 100644
--- a/client/index.html
+++ b/client/index.html
@@ -87,6 +87,7 @@
           <div class="layer" id="layer-fog"></div>
           <div class="layer" id="layer-paths"></div>
           <div class="layer" id="layer-entities"></div>
+          <div class="layer city-label-layer" id="layer-labels"></div>
         </div>
       </div>
 
@@ -129,9 +130,14 @@
           </div>
           <div id="unit-info" class="info-section hidden">
             <div id="unit-name" class="info-title"></div>
+            <div class="unit-stats">
+              <span id="unit-attack" class="unit-stat">Attack —</span>
+              <span id="unit-defense" class="unit-stat">Defense —</span>
+            </div>
             <div class="health-bar"><div id="unit-health-fill"></div></div>
           </div>
         </div>
+        <div id="stat-tooltip" class="tooltip hidden"></div>
       </div>
 
       <!-- Training modal -->
@@ -161,7 +167,7 @@
         </div>
       </div>
 
-      <!-- Nation modal: government and technology tabs -->
+      <!-- Nation modal: government, technology and budget tabs -->
       <div id="modal-nation" class="modal hidden">
         <div class="modal-card">
           <div class="modal-head">
@@ -171,6 +177,7 @@
           <div class="tabs">
             <button class="tab active" data-tab="government">Government</button>
             <button class="tab" data-tab="technology">Technology</button>
+            <button class="tab" data-tab="budget">Budget</button>
           </div>
           <div class="tab-page active" id="tab-government">
             <div id="government-sub" class="modal-sub"></div>
@@ -180,6 +187,10 @@
             <div id="technology-sub" class="modal-sub"></div>
             <div id="technology-list" class="modal-body"></div>
           </div>
+          <div class="tab-page" id="tab-budget">
+            <div id="budget-sub" class="modal-sub"></div>
+            <div id="budget-list" class="modal-body"></div>
+          </div>
         </div>
       </div>
 
diff --git a/client/js/game_screen.js b/client/js/game_screen.js
index 021ed2b..ffac7ef 100644
--- a/client/js/game_screen.js
+++ b/client/js/game_screen.js
@@ -14,6 +14,7 @@ import {
   GOVERNMENTS,
   TECHNOLOGIES,
 } from "../../shared/data.js";
+import { defenseFactors, unitDefense } from "../../shared/rules.js";
 import { dateString } from "../../shared/game_clock.js";
 
 export class GameScreen {
@@ -48,11 +49,14 @@ export class GameScreen {
         fog: $("#layer-fog"),
         paths: $("#layer-paths"),
         entities: $("#layer-entities"),
+        labels: $("#layer-labels"),
       }
     );
     this.trainModal = new TrainModal();
     this.buildingsModal = new BuildingsModal();
     this.nationModal = new NationModal();
+    this.$statTooltip = $("#stat-tooltip");
+    this._hoveredStat = null;
 
     this._bindMap();
     this._bindHud();
@@ -136,9 +140,36 @@ export class GameScreen {
     this.nationModal.onTechnology = (index) =>
       this.sendOrder({ type: "technology", technology: index });
 
+    $("#unit-attack")
+      .on("mouseenter", (event) => this._showStatTooltip($(event.currentTarget)))
+      .on("mouseleave", () => this._hideStatTooltip());
+    $("#unit-defense")
+      .on("mouseenter", (event) => this._showStatTooltip($(event.currentTarget)))
+      .on("mouseleave", () => this._hideStatTooltip());
+
     $(window).on("keydown.game", (event) => this._onKey(event));
   }
 
+  // A small hover tooltip anchored above a stat, fed by its data-tooltip text.
+  _showStatTooltip($stat) {
+    const text = $stat.attr("data-tooltip");
+    if (!text) return;
+    this._hoveredStat = $stat;
+    this.$statTooltip.text(text).removeClass("hidden");
+    const offset = $stat.offset() || { left: 0, top: 0 };
+    const width = this.$statTooltip.outerWidth() || 0;
+    const height = this.$statTooltip.outerHeight() || 0;
+    this.$statTooltip.css({
+      left: `${Math.max(8, offset.left + $stat.outerWidth() / 2 - width / 2)}px`,
+      top: `${Math.max(8, offset.top - height - 8)}px`,
+    });
+  }
+
+  _hideStatTooltip() {
+    this._hoveredStat = null;
+    this.$statTooltip.addClass("hidden");
+  }
+
   _bindMap() {
     this.map.onUnitSelected = (id) => {
       if (!id) {
@@ -204,11 +235,13 @@ export class GameScreen {
   _showUnit(unit) {
     if (!unit) {
       $("#unit-info").addClass("hidden");
+      this._hideStatTooltip();
       this._refreshBottomVisibility();
       return;
     }
     const proto = this.protoUnits[unit.proto];
     $("#unit-name").text(proto ? proto.name : "Unit");
+    this._showUnitStats(unit, proto);
     const ratio = unit.maxHp > 0 ? (unit.hp / unit.maxHp) * 100 : 0;
     $("#unit-health-fill").css("width", `${Math.max(0, Math.min(100, ratio))}%`);
     $("#tile-info, #city-info").addClass("hidden");
@@ -216,6 +249,42 @@ export class GameScreen {
     this._refreshBottomVisibility();
   }
 
+  // Attack and defense of the unit where it stands, with the hovering tooltips
+  // listing each factor that shaped the number.
+  _showUnitStats(unit, proto) {
+    const coords = { x: unit.coords[0], y: unit.coords[1] };
+    const tile = this.map.getTile(coords);
+    const hasCity = ((this.snapshot && this.snapshot.cities) || []).some(
+      (city) => city.coords[0] === coords.x && city.coords[1] === coords.y
+    );
+    const baseAttack = proto && typeof proto.attack === "number" ? proto.attack : 0;
+    const baseDefense = proto && typeof proto.defense === "number" ? proto.defense : 0;
+    const baseRange = proto && typeof proto.range === "number" ? proto.range : 1;
+
+    const attackParts = [`Base ${Math.round(baseAttack)}`];
+    if (baseRange > 1) attackParts.push(`Range ${baseRange}`);
+    $("#unit-attack")
+      .text(`Attack ${Math.round(baseAttack)}`)
+      .attr("data-tooltip", attackParts.join(", "));
+
+    const factors = defenseFactors(tile, hasCity);
+    const defense = unitDefense(baseDefense, tile, hasCity);
+    const parts = [`Base ${Math.round(baseDefense)}`];
+    for (const factor of factors) {
+      parts.push(`${factor.label} +${Math.round(baseDefense * factor.bonus)}`);
+    }
+    $("#unit-defense")
+      .text(`Defense ${Math.round(defense)}`)
+      .attr("data-tooltip", parts.join(", "));
+    // Keep an open tooltip in step with the unit it describes across snapshots.
+    if (this._hoveredStat && !this.$statTooltip.hasClass("hidden")) {
+      const text = this._hoveredStat.attr("data-tooltip");
+      if (text) this.$statTooltip.text(text);
+    } else {
+      this._hideStatTooltip();
+    }
+  }
+
   _showCity(city) {
     if (!city) {
       $("#city-info").addClass("hidden");
@@ -330,14 +399,16 @@ export class GameScreen {
   }
 
   _openNationModal() {
+    const stats = this.snapshot.viewerStats || {};
     this.nationModal.show(
       GOVERNMENTS,
-      (this.snapshot.viewerStats || {}).government || 0,
+      stats.government || 0,
       TECHNOLOGIES,
       this._researched,
-      (this.snapshot.viewerStats || {}).gdp || 0,
-      (this.snapshot.viewerStats || {}).budget || 0,
-      (this.snapshot.viewerStats || {}).research || 0
+      stats.gdp || 0,
+      stats.budget || 0,
+      stats.research || 0,
+      this._finances(stats)
     );
   }
 
@@ -349,10 +420,15 @@ export class GameScreen {
       this._researched,
       stats.gdp || 0,
       stats.budget || 0,
-      stats.research || 0
+      stats.research || 0,
+      this._finances(stats)
     );
   }
 
+  _finances(stats) {
+    return stats.breakdown || null;
+  }
+
   // --------------------------------------------------------------- input ---
 
   _onKey(event) {
diff --git a/client/js/map_view.js b/client/js/map_view.js
index d2d334d..00a3f62 100644
--- a/client/js/map_view.js
+++ b/client/js/map_view.js
@@ -8,7 +8,7 @@ import { MapTopology, mapToLocal, key, COL_STEP, HEX_W, HEX_H } from "../../shar
 import { MapGenerator } from "../../shared/map_generator.js";
 import { TerrainStats } from "../../shared/terrain_stats.js";
 import { HexPathfinder } from "../../shared/hex_pathfinder.js";
-import { MAP_CONFIG, protoUnitById } from "../../shared/data.js";
+import { MAP_CONFIG, protoUnitById, statusById } from "../../shared/data.js";
 
 const RESYNC_HOURS = 0.75;
 const PREDICTION_GRACE_HOURS = 2.0;
@@ -26,6 +26,7 @@ const OVERVIEW_BLOCK = 4;
 const OVERVIEW_COLOURS = {
   Forest: "#2f6b3a",
   Hills: "#7a6a44",
+  Mountain: "#7d7469",
   Ice: "#dcecf5",
   Land: "#4f8a4f",
   Sea: "#1b3f6b",
@@ -52,6 +53,15 @@ export class MapView {
       this.$overview = $('<div id="layer-overview" class="layer overview"></div>');
       this.$world.prepend(this.$overview);
     }
+    // City names live on their own layer above the entities so they are never
+    // hidden behind a unit or city marker.
+    this.$labels = layers.labels && layers.labels.length
+      ? layers.labels
+      : $("#layer-labels");
+    if (!this.$labels.length) {
+      this.$labels = $('<div id="layer-labels" class="layer city-label-layer"></div>');
+      this.$world.append(this.$labels);
+    }
 
     this.seed = -1;
     this.topology = null;
@@ -71,7 +81,9 @@ export class MapView {
 
     this._unitViews = new Map();
     this._unitMotion = new Map();
+    this._unitData = new Map();
     this._cityViews = new Map();
+    this._cityCiv = new Map();
     this._predictNeighbourCache = new Map();
     this._maxStepLength = 1.0;
 
@@ -147,8 +159,12 @@ export class MapView {
     this.$borders.empty();
     this.$fog.empty();
     this.$entities.empty();
+    this.$labels.empty();
     this._unitViews.clear();
+    this._unitMotion.clear();
+    this._unitData.clear();
     this._cityViews.clear();
+    this._cityCiv.clear();
     this._centered = false;
     this._drawOverview(true);
     this._applyWrap(true);
@@ -309,6 +325,7 @@ export class MapView {
 
   _syncCities(cities) {
     const seen = new Set();
+    this._cityCiv = new Map();
     for (const data of cities) {
       const id = data.id;
       seen.add(id);
@@ -318,27 +335,35 @@ export class MapView {
         this._cityViews.set(id, view);
       }
       const coords = { x: data.coords[0], y: data.coords[1] };
+      this._cityCiv.set(key(coords.x, coords.y), data.civ);
       const local = mapToLocal(coords.x, coords.y);
       view._localX = local.x;
       view._localY = local.y;
-      view.style.left = `${local.x + this._wrapShift(local.x)}px`;
+      const wrappedX = local.x + this._wrapShift(local.x);
+      view.style.left = `${wrappedX}px`;
       view.style.top = `${local.y}px`;
       const owned = data.civ === this.localCiv;
-      const label = view.querySelector(".label");
+      const label = view._label;
       label.textContent = data.isCapital ? `${data.name} (capital)` : data.name;
+      label.style.left = `${wrappedX}px`;
+      label.style.top = `${local.y}px`;
       const marker = view.querySelector(".marker");
       marker.style.background = this.civilisations[data.civ]
         ? this.civilisations[data.civ].primaryColour
         : "#444";
       marker.style.cursor = owned ? "pointer" : "default";
       view.dataset.owned = owned ? "1" : "0";
+      this._syncStatusIcons(view.querySelector(".city-statuses"), data.statuses || []);
       // Foreign cities are only shown when their tile has been explored.
       const k = key(coords.x, coords.y);
-      view.style.display = owned || this.explored.has(k) ? "" : "none";
+      const shown = owned || this.explored.has(k);
+      view.style.display = shown ? "" : "none";
+      label.style.display = shown ? "" : "none";
     }
     for (const [id, view] of Array.from(this._cityViews)) {
       if (seen.has(id)) continue;
       view.remove();
+      if (view._label) view._label.remove();
       this._cityViews.delete(id);
     }
   }
@@ -349,15 +374,19 @@ export class MapView {
     const marker = document.createElement("div");
     marker.className = "marker";
     marker.style.backgroundImage = "url(assets/icon_modern_city.svg)";
-    const label = document.createElement("div");
-    label.className = "label";
+    const statuses = document.createElement("div");
+    statuses.className = "city-statuses";
     view.appendChild(marker);
-    view.appendChild(label);
+    view.appendChild(statuses);
     marker.addEventListener("click", (event) => {
       event.stopPropagation();
       if (view.dataset.owned === "1") this.onCitySelected(data.id);
     });
     this.$entities[0].appendChild(view);
+    const label = document.createElement("div");
+    label.className = "city-label";
+    this.$labels[0].appendChild(label);
+    view._label = label;
     return view;
   }
 
@@ -366,6 +395,7 @@ export class MapView {
     for (const data of units) {
       const id = data.id;
       seen.add(id);
+      this._unitData.set(id, data);
       let view = this._unitViews.get(id);
       if (!view) {
         view = this._createUnitView(data);
@@ -374,10 +404,11 @@ export class MapView {
       const proto = this.protoUnits[data.proto];
       const civ = this.civilisations[data.civ];
       view.querySelector(".body").style.background = civ ? civ.primaryColour : "#666";
-      view.querySelector("img").src = proto ? `assets/${proto.icon}` : "assets/person.png";
+      view.querySelector(".body img").src = proto ? `assets/${proto.icon}` : "assets/person.png";
       view.querySelector(".health .fill").style.width =
         `${Math.max(0, Math.min(100, (data.hp / data.maxHp) * 100))}%`;
       view.classList.toggle("selected", id === this._selectedUnitId);
+      this._syncUnitStatuses(view, data);
       this._updateUnitMotion(data);
       // Foreign units are only shown inside currently visible tiles.
       const k = key(data.coords[0], data.coords[1]);
@@ -388,6 +419,7 @@ export class MapView {
       view.remove();
       this._unitViews.delete(id);
       this._unitMotion.delete(id);
+      this._unitData.delete(id);
     }
   }
 
@@ -407,8 +439,11 @@ export class MapView {
     const fill = document.createElement("div");
     fill.className = "fill";
     health.appendChild(fill);
+    const statuses = document.createElement("div");
+    statuses.className = "unit-statuses";
     view.appendChild(body);
     view.appendChild(health);
+    view.appendChild(statuses);
     view.addEventListener("mousedown", (event) => {
       event.stopPropagation();
       if (event.button === 0) this.onUnitSelected(data.id);
@@ -417,6 +452,31 @@ export class MapView {
     return view;
   }
 
+  // Draws one small icon per active status over the unit. The layout is driven
+  // by the snapshot's status ids and the shared catalogue, so a new status
+  // needs only a catalogue entry and an icon file.
+  _syncUnitStatuses(view, data) {
+    this._syncStatusIcons(view.querySelector(".unit-statuses"), data.statuses || []);
+  }
+
+  _syncStatusIcons(container, ids) {
+    if (!container) return;
+    const signature = ids.join(",");
+    if (container._statusSignature === signature) return;
+    container._statusSignature = signature;
+    container.textContent = "";
+    for (const id of ids) {
+      const def = statusById(id);
+      if (!def) continue;
+      const icon = document.createElement("img");
+      icon.className = "status-icon";
+      icon.src = `assets/${def.icon}`;
+      icon.alt = def.label;
+      icon.title = def.description || def.label;
+      container.appendChild(icon);
+    }
+  }
+
   // ------------------------------------------------------------- motion ---
 
   _updateUnitMotion(data) {
@@ -480,8 +540,13 @@ export class MapView {
     }
     for (const view of this._cityViews.values()) {
       if (view._localX === undefined) continue;
-      view.style.left = `${view._localX + this._wrapShift(view._localX)}px`;
+      const left = view._localX + this._wrapShift(view._localX);
+      view.style.left = `${left}px`;
       view.style.top = `${view._localY}px`;
+      if (view._label) {
+        view._label.style.left = `${left}px`;
+        view._label.style.top = `${view._localY}px`;
+      }
     }
   }
 
@@ -893,9 +958,11 @@ export class MapView {
         }
         return this._predictNeighbourCache.get(k);
       },
-      (coords) => {
-        const k = key(coords.x, coords.y);
-        if (!enterCache.has(k)) enterCache.set(k, this._canEnter(civ, proto, coords));
+      (coords, isGoal) => {
+        const k = key(coords.x, coords.y) + (isGoal ? ":goal" : "");
+        if (!enterCache.has(k)) {
+          enterCache.set(k, this._canEnter(civ, proto, coords, unitData.id, isGoal));
+        }
         return enterCache.get(k);
       },
       (_from, to) => {
@@ -915,10 +982,36 @@ export class MapView {
       }
     );
     if (path.length < 2) return null;
+    // The server holds a unit as soon as its target is in range and never
+    // steps onto a living enemy's tile. Mirror that so a ranged unit stops at
+    // its firing distance and a melee one stops beside its opponent.
+    const range = Math.max(1, proto.range || 1);
+    const goalOccupant = this._unitAtCoords(goal, unitData.id);
+    const goalIsEnemy = !!goalOccupant && goalOccupant.civ !== civ &&
+      proto.military === true && this._isMilitaryData(goalOccupant);
+    let route;
+    if (goalIsEnemy) {
+      if (this.topology.tileDistance(start, goal) <= range) return null;
+      const approach = path.slice(0, path.length - 1);
+      let stop = approach.length - 1;
+      for (let i = 1; i < approach.length; i++) {
+        if (this.topology.tileDistance(approach[i], goal) <= range) {
+          stop = i;
+          break;
+        }
+      }
+      route = approach.slice(0, stop + 1);
+    } else {
+      const block = this._firstOccupiedStep(path, unitData.id);
+      route = block >= 1 ? path.slice(0, block) : path;
+    }
+    if (route.length < 2) return null;
     const segmentHours = [];
-    for (let i = 1; i < path.length; i++) segmentHours.push(this._stepHours(proto, civ, path[i]));
+    for (let i = 1; i < route.length; i++) {
+      segmentHours.push(this._stepHours(proto, civ, route[i]));
+    }
     this._unitMotion.set(unitData.id, {
-      path,
+      path: route,
       segmentHours,
       pathHours: 0,
       coords: start,
@@ -926,7 +1019,31 @@ export class MapView {
       predictAge: 0,
     });
     this.animate(0);
-    return path;
+    return route;
+  }
+
+  _isMilitaryData(data) {
+    const proto = this.protoUnits[data.proto];
+    return !!(proto && proto.military);
+  }
+
+  _firstOccupiedStep(path, moverId) {
+    for (let i = 1; i < path.length; i++) {
+      if (this._unitAtCoords(path[i], moverId)) return i;
+    }
+    return -1;
+  }
+
+  _unitAtCoords(coords, ignoreId = 0) {
+    for (const [id, data] of this._unitData) {
+      if (id === ignoreId) continue;
+      const motion = this._unitMotion.get(id);
+      const tile = motion && motion.path.length >= 2
+        ? motion.path[Math.min(pathProgress(motion).index, motion.path.length - 1)]
+        : { x: data.coords[0], y: data.coords[1] };
+      if (tile.x === coords.x && tile.y === coords.y) return data;
+    }
+    return null;
   }
 
   _unitCoords(id) {
@@ -939,12 +1056,27 @@ export class MapView {
     return motion.coords;
   }
 
-  _canEnter(civ, proto, coords) {
+  // Mirrors GameState._canUnitEnter: a hostile unit or city is only a valid
+  // destination (`isGoal`), never a tile to pass through.
+  _canEnter(civ, proto, coords, moverId = 0, isGoal = false) {
     const k = key(coords.x, coords.y);
     if (!this.explored.has(k)) return false;
     const tile = this.tiles[k];
     if (!tile) return false;
-    return proto.traversableTerrains.includes(tile.terrainClass);
+    if (!proto.traversableTerrains.includes(tile.terrainClass)) return false;
+    const occupant = this._unitAtCoords(coords, moverId);
+    if (occupant) {
+      if (occupant.civ === civ) return false;
+      if (!isGoal) return false;
+      const occProto = this.protoUnits[occupant.proto];
+      if (proto.military !== true || !occProto || occProto.military !== true) return false;
+    }
+    const cityCiv = this._cityCiv.get(k);
+    if (cityCiv !== undefined && cityCiv !== civ) {
+      if (!isGoal) return false;
+      if (proto.military !== true) return false;
+    }
+    return true;
   }
 
   _stepHours(proto, civ, coords) {
diff --git a/client/js/modals.js b/client/js/modals.js
index 64db3bb..6af3dc6 100644
--- a/client/js/modals.js
+++ b/client/js/modals.js
@@ -1,6 +1,6 @@
 // The three modal panels of the game HUD: city training, city buildings, and
-// the nation panel (government + technology). They only display state supplied
-// by the game screen and forward the player's choices as orders.
+// the nation panel (government + technology + budget). They only display state
+// supplied by the game screen and forward the player's choices as orders.
 
 import { groupDigits, hours } from "../../shared/text_format.js";
 import { ECONOMY } from "../../shared/data.js";
@@ -33,6 +33,16 @@ function effectsText(effects, level) {
   return parts.length > 0 ? parts.join("   ·   ") : "No effect";
 }
 
+const SOURCE_LABELS = { building: "building", government: "government", technology: "research" };
+
+function signedMoney(value) {
+  return `${value < 0 ? "−" : "+"}€${groupDigits(Math.round(Math.abs(value)))}/h`;
+}
+
+function percent(value) {
+  return `${value < 0 ? "−" : "+"}${(Math.abs(value) * 100).toFixed(1)}%`;
+}
+
 export class TrainModal {
   constructor() {
     this.$modal = $("#modal-train");
@@ -185,12 +195,20 @@ export class NationModal {
     this.$governmentList = $("#government-list");
     this.$technologySub = $("#technology-sub");
     this.$technologyList = $("#technology-list");
+    this.$budgetSub = $("#budget-sub");
+    this.$budgetList = $("#budget-list");
     this.governments = [];
     this.technologies = [];
     this.currentGovernment = 0;
     this.researched = new Set();
     this.governmentRows = [];
     this.technologyRows = [];
+    this.budgetRows = {
+      income: this._makeBudgetRow("Tax income", "State revenue drawn from the nation's GDP."),
+      building: this._makeBudgetRow("Building upkeep", "Upkeep of every building across your cities."),
+      units: this._makeBudgetRow("Military upkeep", "Upkeep of all your units."),
+      net: this._makeBudgetRow("Net balance", "Projected change to the treasury each hour."),
+    };
     this.onGovernment = () => {};
     this.onTechnology = () => {};
     this.$modal.find(".modal-close").on("click", () => this.close());
@@ -207,15 +225,44 @@ export class NationModal {
     return !this.$modal.hasClass("hidden");
   }
 
-  show(governments, currentGovernment, technologies, researched, gdp, budget, research) {
+  show(governments, currentGovernment, technologies, researched, gdp, budget, research, finances) {
     this.governments = governments;
     this.technologies = technologies;
     this.governmentRows = governments.map((proto, index) => this._makeRow(this.$governmentList, proto, index, "government"));
     this.technologyRows = technologies.map((proto, index) => this._makeRow(this.$technologyList, proto, index, "technology"));
-    this.refresh(currentGovernment, researched, gdp, budget, research);
+    this.refresh(currentGovernment, researched, gdp, budget, research, finances);
     this.$modal.removeClass("hidden");
   }
 
+  _makeBudgetRow(name, description) {
+    const $card = $("<div class='row-card'></div>");
+    const $info = $("<div class='info'></div>");
+    const $name = $("<div class='name'></div>").text(name);
+    const $desc = $("<div class='desc'></div>").text(description);
+    const $details = $("<div class='budget-detail'></div>");
+    const $value = $("<div class='value'></div>");
+    $info.append($name, $desc, $details);
+    $card.append($info, $value);
+    this.$budgetList.append($card);
+    return { $value, $details };
+  }
+
+  _renderBudgetRow(row, value, lines) {
+    row.$value
+      .text(signedMoney(value))
+      .toggleClass("positive", value >= 0)
+      .toggleClass("negative", value < 0);
+    row.$details.empty();
+    for (const line of lines) {
+      row.$details.append($("<div class='budget-line'></div>").text(line));
+    }
+  }
+
+  _sourceLines(sources, format, empty) {
+    if (!sources || sources.length === 0) return [empty];
+    return sources.map((source) => format(source));
+  }
+
   _makeRow($list, proto, index, kind) {
     const $card = $("<div class='row-card'></div>");
     const $info = $("<div class='info'></div>");
@@ -236,7 +283,7 @@ export class NationModal {
     return { proto, index, kind, $name, $effects, $cost, $action };
   }
 
-  refresh(currentGovernment, researched, gdp, budget, research) {
+  refresh(currentGovernment, researched, gdp, budget, research, finances = {}) {
     this.currentGovernment = currentGovernment;
     this.researched = researched instanceof Set ? researched : new Set(Object.keys(researched).map(Number));
     this.$governmentSub.text(
@@ -244,6 +291,47 @@ export class NationModal {
     );
     this.$technologySub.text(`Research points: ${groupDigits(Math.round(research))}`);
 
+    const breakdown = finances || {};
+    const income = breakdown.income || { rate: 0, base: 0, modifier: 0, total: 0, sources: [] };
+    const building = breakdown.buildingUpkeep || { total: 0, sources: [] };
+    const units = breakdown.unitUpkeep || { total: 0, sources: [] };
+    const net = breakdown.net || 0;
+
+    this.$budgetSub.text(
+      `Treasury: €${groupDigits(Math.round(budget))}   ·   Net: ${signedMoney(net)}`
+    );
+
+    this._renderBudgetRow(this.budgetRows.income, income.total, [
+      `Tax rate ${(income.rate * 100).toFixed(2)}% of GDP — base €${groupDigits(Math.round(income.base))}/h`,
+      ...this._sourceLines(
+        income.sources,
+        (s) => `${s.label} (${SOURCE_LABELS[s.kind] || s.kind}) ${percent(s.effect)} → ${signedMoney(s.amount)}`,
+        "No bonuses"
+      ),
+    ]);
+    this._renderBudgetRow(
+      this.budgetRows.building,
+      -building.total,
+      this._sourceLines(
+        building.sources,
+        (s) => `${s.label} — €${groupDigits(Math.round(s.amount))}/h`,
+        "No buildings"
+      )
+    );
+    this._renderBudgetRow(
+      this.budgetRows.units,
+      -units.total,
+      this._sourceLines(
+        units.sources,
+        (s) => `${s.label} ×${s.count} — €${groupDigits(Math.round(s.amount))}/h`,
+        "No units"
+      )
+    );
+    this._renderBudgetRow(this.budgetRows.net, net, [
+      `Income ${signedMoney(income.total)}`,
+      `Expenses −€${groupDigits(Math.round(building.total + units.total))}/h`,
+    ]);
+
     for (const row of this.governmentRows) {
       const proto = row.proto;
       row.$name.text(proto.name);
diff --git a/nix/module.nix b/nix/module.nix
index 9d8dbc3..26ef794 100644
--- a/nix/module.nix
+++ b/nix/module.nix
@@ -6,6 +6,15 @@
 #
 # The web client connects to the page's own origin, so nginx serves the static
 # files at "/" and forwards "/ws" to the game server.
+#
+# By default the server runs the immutable copy packaged in the Nix store, so
+# updating the game means rebuilding the system configuration. To update the
+# game on its own instead, point the service at a writable checkout:
+#
+#   services.battle-for-tismo.appDirectory = "/opt/battle-for-tismo";
+#
+# then `git -C /opt/battle-for-tismo pull` and
+# `systemctl restart battle-for-tismo`.
 { config, lib, pkgs, ... }:
 
 let
@@ -16,10 +25,28 @@ in
   options.services.battle-for-tismo = {
     enable = lib.mkEnableOption "the Battle for 'Tismo game server";
 
+    appDirectory = lib.mkOption {
+      type = lib.types.nullOr lib.types.path;
+      default = null;
+      example = "/opt/battle-for-tismo";
+      description = ''
+        Directory containing a writable checkout of the game (`client/`,
+        `server/` and `shared/`). When set, the server runs straight from this
+        directory with the Node.js from Nixpkgs, so the game can be updated
+        with a Git pull and a service restart instead of a system rebuild.
+
+        When null (the default) the immutable copy packaged in the Nix store
+        is used, and updates require a rebuild.
+      '';
+    };
+
     package = lib.mkOption {
       type = lib.types.package;
       default = pkg.server;
-      description = "Package providing the `battle-for-tismo-server` command.";
+      description = ''
+        Package providing the `battle-for-tismo-server` command. Ignored when
+        `appDirectory` is set.
+      '';
     };
 
     port = lib.mkOption {
@@ -41,13 +68,16 @@ in
       enable = lib.mkOption {
         type = lib.types.bool;
         default = true;
-        description = "Serve the exported web client through nginx.";
+        description = "Serve the static web client through nginx.";
       };
 
       package = lib.mkOption {
         type = lib.types.package;
         default = pkg.web;
-        description = "Directory containing the static web client (client/index.html).";
+        description = ''
+          Directory containing the static web client (client/index.html). Point
+          this at the `appDirectory` to serve the mutable checkout as well.
+        '';
       };
 
       hostName = lib.mkOption {
@@ -77,7 +107,12 @@ in
       after = [ "network.target" ];
       environment.HOME = "%S/battle-for-tismo";
       serviceConfig = {
-        ExecStart = "${cfg.package}/bin/battle-for-tismo-server --port ${toString cfg.port} --bind ${cfg.bindAddress}";
+        ExecStart =
+          if cfg.appDirectory != null then
+            "${pkgs.nodejs}/bin/node ${toString cfg.appDirectory}/server/server.js"
+            + " --port ${toString cfg.port} --bind ${cfg.bindAddress}"
+          else
+            "${cfg.package}/bin/battle-for-tismo-server --port ${toString cfg.port} --bind ${cfg.bindAddress}";
         DynamicUser = true;
         StateDirectory = "battle-for-tismo";
         Restart = "on-failure";
diff --git a/shared/data.js b/shared/data.js
index dd158a5..daaab5d 100644
--- a/shared/data.js
+++ b/shared/data.js
@@ -91,20 +91,24 @@ export const CIVILISATIONS = [
   },
 ];
 
-export const CITY_DESCRIPTIONS = {
-  france: { name: "Paris", population: 11200000, improvements: ["Eiffel Tower", "Louvre", "Notre-Dame"] },
-  britain: { name: "London", population: 9500000, improvements: ["Big Ben", "Tower Bridge", "Buckingham Palace"] },
-};
-
 export const PROTO_UNITS = [
   {
     id: "modern_infantry",
     name: "Modern infantry",
     maxHp: 500,
-    cost: 500000,
-    upkeep: 50000000,
+    cost: 100_000_000,
+    upkeep: 5000,
     moveable: true,
     speed: 0.5,
+    // Only military units fight, capture cities and may enter an enemy
+    // military unit's tile. `attack` is the damage dealt per combat round and
+    // `defense` is the damage absorbed per round; a defender's defense is
+    // doubled (the 100% defensive bonus). `range` is how many tiles away the
+    // unit can strike (1 is melee).
+    military: true,
+    attack: 100,
+    defense: 40,
+    range: 1,
     traversableTerrains: ["Land"],
     icon: "icon_modern_infantry.svg",
   },
@@ -116,14 +120,65 @@ export const PROTO_UNITS = [
     upkeep: 0,
     moveable: true,
     speed: 0.5,
+    military: false,
+    attack: 0,
+    defense: 0,
+    range: 1,
     traversableTerrains: ["Land"],
     icon: "icon_settler.svg",
   },
+  {
+    id: "artillery",
+    name: "Artillery",
+    maxHp: 400,
+    cost: 300_000_000,
+    upkeep: 12_000,
+    moveable: true,
+    speed: 0.25,
+    military: true,
+    attack: 250,
+    // Barely armoured: nearly every hit gets through.
+    defense: 5,
+    // Outranges infantry, so melee units cannot strike back from two tiles.
+    range: 2,
+    traversableTerrains: ["Land"],
+    icon: "icon_artillery.svg",
+  },
 ];
 
 // Only units in this list can be trained from the city screen, matching
 // GameState.TRAINABLE_UNITS.
-export const TRAINABLE_UNIT_IDS = ["modern_infantry"];
+export const TRAINABLE_UNIT_IDS = ["modern_infantry", "artillery"];
+
+// Status effects a unit or city can carry. They are data-driven so new ones
+// can be added without touching the simulation or the renderer: the server
+// derives the active ids once a day, applies their daily fields, and ships the
+// ids in snapshots; the browser draws one icon per id. A status may define
+// `hpLossPerDay` (a fraction of maximum hit points taken each day) and a
+// `cityHpLossPerDay` override for when the unit stands in a city.
+export const STATUS_ENCIRCLED = "encircled";
+export const STATUS_BESIEGED = "besieged";
+
+export const STATUSES = [
+  {
+    id: STATUS_ENCIRCLED,
+    label: "Encircled",
+    icon: "encirclement.svg",
+    description: "Cut off from every allied city while a hostile unit is adjacent. Loses 10% of its maximum hit points each day, or 2% inside a city.",
+    hpLossPerDay: 0.10,
+    cityHpLossPerDay: 0.02,
+  },
+  {
+    id: STATUS_BESIEGED,
+    label: "Besieged",
+    icon: "encirclement.svg",
+    description: "Cut off from every other allied city while a hostile unit is adjacent.",
+  },
+];
+
+export function statusById(id) {
+  return STATUSES.find((status) => status.id === id) || null;
+}
 
 export const BUILDINGS = [
   {
@@ -283,12 +338,12 @@ export const TECHNOLOGIES = [
 ];
 
 export const ECONOMY = {
-  baseGdpPerCapita: 10000,
-  basePopulation: 100000,
+  baseGdpPerCapita: 10_000,
+  basePopulation: 100_000,
   cityTileGdpMultiplier: 2.0,
   capitalTileGdpMultiplier: 2.5,
   citySurroundingGdpBonus: 0.3,
-  gdpPerProductionPoint: 100000000,
+  gdpPerProductionPoint: 100_000,
   budgetGdpRate: 0.001,
   startingBudget: 0,
   basePopulationGrowthRate: 0.005,
@@ -338,17 +393,22 @@ export const MAP_CONFIG = {
 
 // The terrain TileSet, flattened. `col` is the atlas column in terrain.png
 // (one row, 7 tiles of 63x56); the class decides land/sea/ice and the
-// minElevation bands place land tiles.
+// minElevation bands place land tiles. `defenseBonus` is the fraction added to
+// a unit's defense while it stands on the tile.
 export const TERRAIN_TILES = [
-  { col: 0, terrainType: "Forest", terrainClass: "Land", populationMultiplier: 0.3, gdpMultiplier: 0.5, movementCostMultiplier: 1.5, minElevation: 0.06 },
-  { col: 1, terrainType: "Hills", terrainClass: "Land", populationMultiplier: 0.7, gdpMultiplier: 0.8, movementCostMultiplier: 1.8, minElevation: 0.2 },
-  { col: 2, terrainType: "Ice", terrainClass: "Ice", populationMultiplier: 0, gdpMultiplier: 0, movementCostMultiplier: 4.0, minElevation: 0 },
-  { col: 3, terrainType: "Land", terrainClass: "Land", populationMultiplier: 1.0, gdpMultiplier: 1.0, movementCostMultiplier: 1.0, minElevation: -0.08 },
-  { col: 4, terrainType: "Land", terrainClass: "Land", populationMultiplier: 0.05, gdpMultiplier: 0.2, movementCostMultiplier: 3.0, minElevation: -0.2 },
-  { col: 5, terrainType: "Sea", terrainClass: "Sea", populationMultiplier: 0, gdpMultiplier: 0, movementCostMultiplier: 0, minElevation: 0 },
-  { col: 6, terrainType: "Land", terrainClass: "Land", populationMultiplier: 0.1, gdpMultiplier: 0.8, movementCostMultiplier: 5.0, minElevation: 0.34 },
+  { col: 0, terrainType: "Forest", terrainClass: "Land", populationMultiplier: 0.3, gdpMultiplier: 0.5, movementCostMultiplier: 1.5, defenseBonus: 0.33, minElevation: 0.06 },
+  { col: 1, terrainType: "Hills", terrainClass: "Land", populationMultiplier: 0.7, gdpMultiplier: 0.8, movementCostMultiplier: 1.8, defenseBonus: 0.33, minElevation: 0.2 },
+  { col: 2, terrainType: "Ice", terrainClass: "Ice", populationMultiplier: 0, gdpMultiplier: 0, movementCostMultiplier: 4.0, defenseBonus: 0, minElevation: 0 },
+  { col: 3, terrainType: "Land", terrainClass: "Land", populationMultiplier: 1.0, gdpMultiplier: 1.0, movementCostMultiplier: 1.0, defenseBonus: 0, minElevation: -0.08 },
+  { col: 4, terrainType: "Land", terrainClass: "Land", populationMultiplier: 0.05, gdpMultiplier: 0.2, movementCostMultiplier: 3.0, defenseBonus: 0, minElevation: -0.2 },
+  { col: 5, terrainType: "Sea", terrainClass: "Sea", populationMultiplier: 0, gdpMultiplier: 0, movementCostMultiplier: 0, defenseBonus: 0, minElevation: 0 },
+  { col: 6, terrainType: "Mountain", terrainClass: "Land", populationMultiplier: 0.1, gdpMultiplier: 0.8, movementCostMultiplier: 5.0, defenseBonus: 1.0, minElevation: 0.34 },
 ];
 
+// A city standing on a tile adds this fraction on top of the terrain's own
+// defensive bonus.
+export const CITY_DEFENSE_BONUS = 0.5;
+
 export function protoUnitById(id) {
   return PROTO_UNITS.find((u) => u.id === id) || null;
 }
diff --git a/shared/game_state.js b/shared/game_state.js
index b1ec004..b924032 100644
--- a/shared/game_state.js
+++ b/shared/game_state.js
@@ -17,13 +17,15 @@ import {
   BUILDINGS,
   GOVERNMENTS,
   TECHNOLOGIES,
-  CITY_DESCRIPTIONS,
   EFFECT_GDP,
   EFFECT_BUDGET_INCOME,
   EFFECT_RESEARCH,
   EFFECT_CULTURE,
+  STATUS_ENCIRCLED,
+  STATUS_BESIEGED,
+  statusById,
 } from "./data.js";
-import { buildingBuildCost, buildingRefund, buildingUpkeep, prerequisitesMet } from "./rules.js";
+import { buildingBuildCost, buildingRefund, buildingUpkeep, prerequisitesMet, defenseMultiplier } from "./rules.js";
 
 export const UNIT_VISION = 2;
 export const TERRITORY_VISION = 1;
@@ -33,6 +35,8 @@ export const HOURS_PER_YEAR = HOURS_PER_DAY * DAYS_PER_YEAR;
 export const CONTROLLED_SPEED_MULTIPLIER = 1.5;
 export const DEFAULT_UNIT_SPEED = 0.5;
 export const MIN_STEP_COST = 0.0001;
+// A defending unit's defense is doubled: a 100% defensive bonus.
+export const DEFENDER_DEFENSE_MULTIPLIER = 2.0;
 
 export class GameState {
   constructor() {
@@ -147,6 +151,7 @@ export class GameState {
     this._configured = true;
 
     this._placeSettlements();
+    this._refreshStatuses();
     this._revealAll();
     this._refreshVisibility();
     this._visibilityDirty = false;
@@ -234,8 +239,18 @@ export class GameState {
     if (!unit) return false;
     const proto = this.unitProto(unit);
     if (!proto || !proto.moveable) return false;
+    // Ordering a move onto an enemy military unit is an attack: remember the
+    // target so the unit stops as soon as it is within range instead of walking
+    // all the way into it.
+    const target = this.unitAt(goal);
+    const attacking = !!target && target !== unit && target.civ !== unit.civ &&
+      this._isMilitary(unit) && this._isMilitary(target);
+    unit.attackTarget = attacking ? target.id : null;
     const path = this.findPath(unit, unit.coords, goal);
-    if (path.length < 2) return false;
+    if (path.length < 2) {
+      unit.attackTarget = null;
+      return false;
+    }
     unit.path = path;
     unit.pathIndex = 0;
     unit.progressHours = 0;
@@ -250,12 +265,23 @@ export class GameState {
 
   advanceMovement(hours) {
     if (hours <= 0) return;
+    // Units in contact are locked in place until the daily combat round
+    // resolves, so neither side can slip away mid-fight.
+    const engaged = this._engagedUnits();
     for (const unit of this.units) {
       const path = unit.path;
       if (!path || path.length === 0) continue;
+      if (engaged.has(unit)) continue;
       let hoursLeft = hours;
       while (hoursLeft > 0 && unit.pathIndex < path.length - 1) {
+        // Stop as soon as the target is in range: a ranged unit holds its
+        // distance rather than closing to melee.
+        if (this._combatTarget(unit)) break;
         const next = path[unit.pathIndex + 1];
+        // Any other unit on the next tile blocks the step. Military pairs are
+        // resolved by the daily combat round instead; the rest simply wait.
+        const occupant = this.unitAt(next);
+        if (occupant && occupant !== unit) break;
         const cost = Math.max(this._tileTravelHours(unit, next), MIN_STEP_COST);
         const needed = cost - unit.progressHours;
         if (hoursLeft >= needed) {
@@ -264,6 +290,7 @@ export class GameState {
           unit.progressHours = 0;
           unit.coords = next;
           this._visibilityDirty = true;
+          this._onUnitArrived(unit);
         } else {
           unit.progressHours += hoursLeft;
           hoursLeft = 0;
@@ -277,6 +304,309 @@ export class GameState {
     }
   }
 
+  _engagedUnits() {
+    const engaged = new Set();
+    for (const { attacker, defender } of this._combatPairs()) {
+      engaged.add(attacker);
+      // A defender that cannot strike back (an out-ranged melee unit) is free
+      // to keep moving; one that is in reach is locked in the exchange.
+      if (this._canReach(defender, attacker)) engaged.add(defender);
+    }
+    return engaged;
+  }
+
+  _canReach(unit, target) {
+    return this.topology.tileDistance(unit.coords, target.coords) <= this._unitRange(unit);
+  }
+
+  // Unique attacker/defender pairs, so two units that ordered moves into each
+  // other fight one round rather than two. The lower id is the attacker.
+  _combatPairs() {
+    const pairs = new Map();
+    for (const unit of this.units) {
+      const defender = this._combatTarget(unit);
+      if (!defender) continue;
+      const pairKey = unit.id < defender.id
+        ? `${unit.id}:${defender.id}`
+        : `${defender.id}:${unit.id}`;
+      if (!pairs.has(pairKey)) pairs.set(pairKey, { attacker: unit, defender });
+    }
+    return Array.from(pairs.values());
+  }
+
+  // The enemy military unit the given unit is attacking, or null. A unit
+  // attacks the target it was ordered onto, falling back to whatever occupies
+  // the next step of its path; either way the target must be within range.
+  _combatTarget(unit) {
+    if (!this._isMilitary(unit)) return null;
+    let target = unit.attackTarget ? this.findUnit(unit.attackTarget) : null;
+    if (!target) {
+      const next = this._nextStepTile(unit);
+      if (!next) return null;
+      target = this.unitAt(next);
+    }
+    if (!target || target === unit) return null;
+    if (target.civ === unit.civ || !this._isMilitary(target)) return null;
+    if (this.topology.tileDistance(unit.coords, target.coords) > this._unitRange(unit)) return null;
+    return target;
+  }
+
+  _unitRange(unit) {
+    const proto = this.unitProto(unit);
+    return proto && typeof proto.range === "number" ? proto.range : 1;
+  }
+
+  // Recomputes the status of every unit and city. The supply search only runs
+  // for an occupant that has a hostile unit adjacent, and only once a day (and
+  // at setup), so it never touches the snapshot path.
+  _refreshStatuses() {
+    const components = new Map();
+    for (const unit of this.units) {
+      if (!this._hasAdjacentHostile(unit.coords, unit.civ)) {
+        unit.statuses = [];
+        continue;
+      }
+      unit.statuses = this._unitStatuses(unit, this._componentsFor(components, unit.civ));
+    }
+    for (const city of this.cities) {
+      if (!this._hasAdjacentHostile(city.coords, city.civ)) {
+        city.statuses = [];
+        continue;
+      }
+      city.statuses = this._cityStatuses(city, this._componentsFor(components, city.civ));
+    }
+  }
+
+  // The trigger: encirclement is only evaluated when a hostile unit is next to
+  // the tile.
+  _hasAdjacentHostile(coords, civ) {
+    for (const neighbour of this._neighbours(coords)) {
+      const occupant = this.unitAt(neighbour);
+      if (occupant && occupant.civ !== civ) return true;
+    }
+    return false;
+  }
+
+  _componentsFor(cache, civ) {
+    if (!cache.has(civ)) cache.set(civ, this._landComponents(civ));
+    return cache.get(civ);
+  }
+
+  _isNaval(unit) {
+    const proto = this.unitProto(unit);
+    return !!(proto && proto.traversableTerrains.includes("Sea"));
+  }
+
+  // Land connected components for one civ, with enemy-occupied and enemy-held
+  // city tiles acting as walls. Each component remembers how many of the civ's
+  // cities it contains, which is all the supply check needs.
+  _landComponents(civ) {
+    const byTile = new Map();
+    const cityCountByComp = new Map();
+    const totalCities = this.cities.filter((city) => city.civ === civ).length;
+    let component = 0;
+    for (const start of this.landCells) {
+      const startKey = key(start.x, start.y);
+      if (byTile.has(startKey) || !this._landPassable(start, civ)) continue;
+      const id = component++;
+      byTile.set(startKey, id);
+      let cities = 0;
+      let frontier = [start];
+      while (frontier.length > 0) {
+        const next = [];
+        for (const coords of frontier) {
+          const city = this.cityAt(coords);
+          if (city && city.civ === civ) cities += 1;
+          for (const neighbour of this._neighbours(coords)) {
+            const nk = key(neighbour.x, neighbour.y);
+            if (byTile.has(nk) || !this._landPassable(neighbour, civ)) continue;
+            byTile.set(nk, id);
+            next.push(neighbour);
+          }
+        }
+        frontier = next;
+      }
+      cityCountByComp.set(id, cities);
+    }
+    return { byTile, cityCountByComp, totalCities };
+  }
+
+  _landPassable(coords, civ) {
+    const tile = this.tiles[key(coords.x, coords.y)];
+    if (!tile || tile.terrainClass !== "Land") return false;
+    const occupant = this.unitAt(coords);
+    if (occupant && occupant.civ !== civ) return false;
+    const city = this.cityAt(coords);
+    if (city && city.civ !== civ) return false;
+    return true;
+  }
+
+  // A city is besieged when it no longer shares a land component with any
+  // other city of its civ. A lone city is never besieged.
+  _isCityBesieged(city, info) {
+    if (info.totalCities < 2) return false;
+    const component = info.byTile.get(key(city.coords.x, city.coords.y));
+    const count = component === undefined ? 0 : (info.cityCountByComp.get(component) || 0);
+    return count <= 1;
+  }
+
+  _unitStatuses(unit, info) {
+    const city = this.cityAt(unit.coords);
+    const inOwnCity = city && city.civ === unit.civ;
+    let encircled;
+    if (inOwnCity) {
+      encircled = this._isCityBesieged(city, info);
+    } else {
+      const component = info.byTile.get(key(unit.coords.x, unit.coords.y));
+      const count = component === undefined ? 0 : (info.cityCountByComp.get(component) || 0);
+      encircled = count === 0;
+    }
+    const excludeCity = inOwnCity ? city.id : 0;
+    if (encircled && this._hasMaritimeRoute(unit.coords, unit.civ, excludeCity)) {
+      encircled = false;
+    }
+    return encircled ? [STATUS_ENCIRCLED] : [];
+  }
+
+  _cityStatuses(city, info) {
+    const besieged = this._isCityBesieged(city, info) &&
+      !this._hasMaritimeRoute(city.coords, city.civ, city.id);
+    return besieged ? [STATUS_BESIEGED] : [];
+  }
+
+  // The maritime exception: with an allied naval unit on an adjacent sea tile,
+  // a lane is traced across water to a different coastal allied city. Enemy
+  // units on the water block it.
+  _hasMaritimeRoute(origin, civ, excludeCityId) {
+    const visited = new Set();
+    let frontier = [];
+    for (const neighbour of this._neighbours(origin)) {
+      const tile = this.tiles[key(neighbour.x, neighbour.y)];
+      if (!tile || tile.terrainClass !== "Sea") continue;
+      const occupant = this.unitAt(neighbour);
+      if (!occupant || occupant.civ !== civ || !this._isNaval(occupant)) continue;
+      const nk = key(neighbour.x, neighbour.y);
+      if (visited.has(nk)) continue;
+      visited.add(nk);
+      frontier.push(neighbour);
+    }
+    while (frontier.length > 0) {
+      const next = [];
+      for (const coords of frontier) {
+        for (const neighbour of this._neighbours(coords)) {
+          const city = this.cityAt(neighbour);
+          if (city && city.civ === civ && city.id !== excludeCityId) return true;
+        }
+        for (const neighbour of this._neighbours(coords)) {
+          const tile = this.tiles[key(neighbour.x, neighbour.y)];
+          if (!tile || tile.terrainClass !== "Sea") continue;
+          const nk = key(neighbour.x, neighbour.y);
+          if (visited.has(nk)) continue;
+          const occupant = this.unitAt(neighbour);
+          if (occupant && occupant.civ !== civ) continue;
+          visited.add(nk);
+          next.push(neighbour);
+        }
+      }
+      frontier = next;
+    }
+    return false;
+  }
+
+  _statusHpLossPerDay(def, inCity) {
+    if (inCity && typeof def.cityHpLossPerDay === "number") return def.cityHpLossPerDay;
+    return typeof def.hpLossPerDay === "number" ? def.hpLossPerDay : 0;
+  }
+
+  // Applies every active status once per day. The only effect so far is
+  // attrition, but the loop is generic so new daily fields slot in here.
+  _applyDailyStatusEffects() {
+    const damage = new Map();
+    for (const unit of this.units) {
+      const statuses = unit.statuses || [];
+      if (statuses.length === 0) continue;
+      const inCity = !!this.cityAt(unit.coords);
+      let fraction = 0;
+      for (const id of statuses) {
+        const def = statusById(id);
+        if (def) fraction += this._statusHpLossPerDay(def, inCity);
+      }
+      if (fraction > 0) damage.set(unit, unit.maxHp * fraction);
+    }
+    if (damage.size === 0) return;
+    const destroyed = [];
+    for (const [unit, amount] of damage) {
+      unit.hp -= amount;
+      if (unit.hp <= 0) {
+        unit.hp = 0;
+        destroyed.push(unit);
+      }
+    }
+    for (const unit of destroyed) this._destroyUnit(unit);
+    if (destroyed.length > 0) this._visibilityDirty = true;
+    this._emitChanged();
+  }
+
+  _nextStepTile(unit) {
+    const path = unit.path;
+    if (!path || path.length < 2) return null;
+    if (unit.pathIndex + 1 >= path.length) return null;
+    return path[unit.pathIndex + 1];
+  }
+
+  // One combat round: at most one per day, resolved in `tickHour`. Both sides
+  // trade blows and damage lands simultaneously, so a mutual kill destroys both
+  // units.
+  _resolveCombatRound() {
+    const damage = new Map();
+    for (const { attacker, defender } of this._combatPairs()) {
+      const distance = this.topology.tileDistance(attacker.coords, defender.coords);
+      const toDefender = Math.max(
+        1,
+        this._unitAttack(attacker) - this._effectiveDefense(defender, true)
+      );
+      damage.set(defender, (damage.get(defender) || 0) + toDefender);
+      // Only return fire when the attacker is inside the defender's own range,
+      // so an out-ranged melee unit cannot reach an artillery piece.
+      if (distance <= this._unitRange(defender)) {
+        const toAttacker = Math.max(
+          1,
+          this._unitAttack(defender) - this._effectiveDefense(attacker, false)
+        );
+        damage.set(attacker, (damage.get(attacker) || 0) + toAttacker);
+      }
+    }
+    if (damage.size === 0) return;
+    const destroyed = [];
+    for (const [unit, amount] of damage) {
+      unit.hp -= amount;
+      if (unit.hp <= 0) {
+        unit.hp = 0;
+        destroyed.push(unit);
+      }
+    }
+    for (const unit of destroyed) this._destroyUnit(unit);
+    if (destroyed.length > 0) {
+      this._visibilityDirty = true;
+      this._emitChanged();
+    }
+  }
+
+  _destroyUnit(unit) {
+    const index = this.units.indexOf(unit);
+    if (index >= 0) this.units.splice(index, 1);
+    this._unitById.delete(unit.id);
+  }
+
+  // Called when a unit finishes stepping onto a tile. A military unit entering
+  // an enemy city captures it.
+  _onUnitArrived(unit) {
+    const city = this._cityByCoords.get(key(unit.coords.x, unit.coords.y));
+    if (city && city.civ !== unit.civ && this._isMilitary(unit)) {
+      this._captureCity(city, unit.civ);
+    }
+  }
+
   tickHour() {
     this.totalHours += 1;
     this._tickTraining();
@@ -287,6 +617,9 @@ export class GameState {
     if (this.totalHours % HOURS_PER_DAY === 0) {
       this._tickPopulation();
       this._tickEconomy();
+      this._refreshStatuses();
+      this._applyDailyStatusEffects();
+      this._resolveCombatRound();
     }
     this._tickBuildings();
     this._emitChanged();
@@ -412,6 +745,106 @@ export class GameState {
     return city.buildings[protoIndex] || 0;
   }
 
+  // Income and upkeep with the source behind every figure, so the UI can show
+  // which buildings, government or technologies shape the budget. Amounts are
+  // per in-game hour, matching the rest of the economy figures.
+  budgetBreakdown(civ) {
+    const gdp = this.getPlayerGdp(civ);
+    const rate = ECONOMY.budgetGdpRate;
+    const base = gdp * rate;
+    const incomeSources = this._incomeSources(civ);
+    const modifier = incomeSources.reduce((sum, source) => sum + source.effect, 0);
+    const income = base * (1 + modifier);
+    const buildingSources = this._buildingUpkeepSources(civ, gdp);
+    const buildingUpkeep = buildingSources.reduce((sum, source) => sum + source.amount, 0);
+    const unitSources = this._unitUpkeepSources(civ);
+    const unitUpkeep = unitSources.reduce((sum, source) => sum + source.amount, 0);
+    return {
+      income: {
+        rate,
+        base,
+        modifier,
+        total: income,
+        sources: incomeSources.map((source) => ({ ...source, amount: base * source.effect })),
+      },
+      buildingUpkeep: { total: buildingUpkeep, sources: buildingSources },
+      unitUpkeep: { total: unitUpkeep, sources: unitSources },
+      net: income - buildingUpkeep - unitUpkeep,
+    };
+  }
+
+  // Every building, government and researched technology that shifts budget
+  // income, combined per source and expressed as a fraction of the base take.
+  _incomeSources(civ) {
+    const sources = new Map();
+    const add = (label, kind, effect) => {
+      if (effect === 0) return;
+      const k = `${kind}:${label}`;
+      const entry = sources.get(k) || { label, kind, effect: 0 };
+      entry.effect += effect;
+      sources.set(k, entry);
+    };
+    for (const city of this.cities) {
+      if (city.civ !== civ) continue;
+      for (const indexStr of Object.keys(city.buildings)) {
+        const proto = this.protoBuildings[Number(indexStr)];
+        const level = city.buildings[indexStr];
+        for (const e of proto.effects) {
+          if (e.stat === EFFECT_BUDGET_INCOME) add(proto.name, "building", effectAt(e, level));
+        }
+      }
+    }
+    const government = this.governments[this.getGovernment(civ)];
+    if (government) {
+      for (const e of government.effects) {
+        if (e.stat === EFFECT_BUDGET_INCOME) add(government.name, "government", effectAt(e, 1));
+      }
+    }
+    const researched = this.researched.get(civ) || new Set();
+    for (const index of researched) {
+      const tech = this.technologies[index];
+      for (const e of tech.effects) {
+        if (e.stat === EFFECT_BUDGET_INCOME) add(tech.name, "technology", effectAt(e, 1));
+      }
+    }
+    return this._sortSources(Array.from(sources.values()));
+  }
+
+  _buildingUpkeepSources(civ, gdp) {
+    const sources = new Map();
+    for (const city of this.cities) {
+      if (city.civ !== civ) continue;
+      for (const indexStr of Object.keys(city.buildings)) {
+        const index = Number(indexStr);
+        const amount = buildingUpkeep(this.protoBuildings[index], gdp, city.buildings[indexStr]);
+        if (amount === 0) continue;
+        const entry = sources.get(index) || { label: this.protoBuildings[index].name, kind: "building", amount: 0 };
+        entry.amount += amount;
+        sources.set(index, entry);
+      }
+    }
+    return this._sortSources(Array.from(sources.values()));
+  }
+
+  _unitUpkeepSources(civ) {
+    const sources = new Map();
+    for (const unit of this.units) {
+      if (unit.civ !== civ) continue;
+      const proto = this.unitProto(unit);
+      if (!proto || !proto.upkeep) continue;
+      const entry = sources.get(unit.proto) || { label: proto.name, kind: "unit", amount: 0, count: 0 };
+      entry.amount += proto.upkeep;
+      entry.count += 1;
+      sources.set(unit.proto, entry);
+    }
+    return this._sortSources(Array.from(sources.values()));
+  }
+
+  _sortSources(sources) {
+    const weight = (source) => (source.amount !== undefined ? source.amount : source.effect);
+    return sources.sort((a, b) => weight(b) - weight(a));
+  }
+
   getCivBuildingModifiers(civ) {
     const totals = {};
     for (const city of this.cities) {
@@ -519,6 +952,64 @@ export class GameState {
     return proto.traversableTerrains.includes(tile.terrainClass);
   }
 
+  // Whether `unit` may occupy `coords`: passable terrain, no friendly unit in
+  // the way and no enemy unit there unless both are military (which turns the
+  // step into a fight). Enemy cities are only open to military units, since
+  // walking one in captures it.
+  //
+  // A hostile unit or city is only a valid destination (`isGoal`), never a tile
+  // to pass through: pathfinding routes around enemies instead of through them.
+  _canUnitEnter(unit, coords, isGoal = false) {
+    const proto = this.unitProto(unit);
+    if (!this.canEnter(unit.civ, proto, coords)) return false;
+    const occupant = this.unitAt(coords);
+    if (occupant && occupant !== unit) {
+      if (occupant.civ === unit.civ) return false;
+      if (!isGoal) return false;
+      if (!this._isMilitary(unit) || !this._isMilitary(occupant)) return false;
+    }
+    const city = this._cityByCoords.get(key(coords.x, coords.y));
+    if (city && city.civ !== unit.civ) {
+      if (!isGoal) return false;
+      if (!this._isMilitary(unit)) return false;
+    }
+    return true;
+  }
+
+  isMilitary(unit) {
+    return this._isMilitary(unit);
+  }
+
+  _isMilitary(unit) {
+    const proto = this.unitProto(unit);
+    return !!(proto && proto.military);
+  }
+
+  _unitAttack(unit) {
+    const proto = this.unitProto(unit);
+    return proto && typeof proto.attack === "number" ? proto.attack : 0;
+  }
+
+  _unitDefense(unit) {
+    const proto = this.unitProto(unit);
+    return proto && typeof proto.defense === "number" ? proto.defense : 0;
+  }
+
+  // Fraction of extra defense granted by the tile a unit occupies (terrain
+  // plus any city), as a multiplier.
+  _defenseMultiplierAt(coords) {
+    const tile = this.tiles[key(coords.x, coords.y)];
+    return defenseMultiplier(tile, !!this.cityAt(coords));
+  }
+
+  // A unit's base defense, boosted by its tile, and doubled when it is the
+  // defending side of the exchange.
+  _effectiveDefense(unit, isDefender) {
+    let defense = this._unitDefense(unit) * this._defenseMultiplierAt(unit.coords);
+    if (isDefender) defense *= DEFENDER_DEFENSE_MULTIPLIER;
+    return defense;
+  }
+
   findPath(unit, start, goal) {
     const proto = this.unitProto(unit);
     const civ = unit.civ;
@@ -529,9 +1020,9 @@ export class GameState {
       start,
       goal,
       (coords) => this._neighbours(coords),
-      (coords) => {
-        const k = key(coords.x, coords.y);
-        if (!enterCache.has(k)) enterCache.set(k, this.canEnter(civ, proto, coords));
+      (coords, isGoal) => {
+        const k = key(coords.x, coords.y) + (isGoal ? ":goal" : "");
+        if (!enterCache.has(k)) enterCache.set(k, this._canUnitEnter(unit, coords, isGoal));
         return enterCache.get(k);
       },
       (_from, to) => {
@@ -584,17 +1075,14 @@ export class GameState {
       population: description.population,
       improvements: description.improvements.slice(),
       buildings: {},
+      statuses: [],
     };
     this.cities.push(city);
     this._cityById.set(this._nextCityId, city);
     this._nextCityId += 1;
   }
 
-  _cityDescriptionFor(civ, isCapital, center) {
-    if (isCapital && CITY_DESCRIPTIONS[civ.id]) {
-      const named = CITY_DESCRIPTIONS[civ.id];
-      return { name: named.name, population: named.population, improvements: named.improvements };
-    }
+  _cityDescriptionFor(civ, _isCapital, center) {
     return this._generatedCityDescription(civ, center);
   }
 
@@ -639,10 +1127,13 @@ export class GameState {
       path: [],
       pathIndex: 0,
       progressHours: 0,
+      attackTarget: null,
+      statuses: [],
     };
     this.units.push(unit);
     this._unitById.set(this._nextUnitId, unit);
     this._nextUnitId += 1;
+    return unit;
   }
 
   _recomputeTerritory() {
@@ -678,6 +1169,86 @@ export class GameState {
     this._serializedTerritory = serializeCells(this.territory);
   }
 
+  // Rebuilds the owner index, the serialised territory and the GDP-per-capita
+  // cache after `this.territory` changes outside a full recompute.
+  _reindexTerritory() {
+    this._territoryByCiv = new Map();
+    for (const [k, owner] of this.territory) {
+      if (!this._territoryByCiv.has(owner)) this._territoryByCiv.set(owner, []);
+      this._territoryByCiv.get(owner).push(parseKey(k));
+    }
+    this._serializedTerritory = serializeCells(this.territory);
+    this._gdpPerCapitaCache = new Map();
+  }
+
+  // Transfers `city` to `newCiv` and, with it, every tile of the old owner's
+  // territory that is strictly closer (through land) to the captured city than
+  // to any of their remaining cities. Ties stay with the old owner.
+  _captureCity(city, newCiv) {
+    const oldCiv = city.civ;
+    if (oldCiv === newCiv) return false;
+    const region = (this._territoryByCiv.get(oldCiv) || []).slice();
+    const claim = this._nearestCityOwner(city, oldCiv, newCiv);
+    city.civ = newCiv;
+    for (const coords of region) {
+      const k = key(coords.x, coords.y);
+      if (claim.get(k) === newCiv) this.territory.set(k, newCiv);
+    }
+    // The captured city's own tile always changes hands, ties or not.
+    this.territory.set(key(city.coords.x, city.coords.y), newCiv);
+    this.training.delete(city.id);
+    this._reindexTerritory();
+    this._rebuildCityIndex();
+    this._visibilityDirty = true;
+    this._emitChanged();
+    return true;
+  }
+
+  // Multi-source BFS over land from the captured city and every remaining city
+  // of the old owner. Each tile records the civ of the nearest city; a tile
+  // reached at the same distance from both sides is credited to the old owner.
+  _nearestCityOwner(captured, oldCiv, newCiv) {
+    const claim = new Map();
+    const visited = new Set();
+    let frontier = [];
+    const sources = [{ coords: captured.coords, civ: newCiv }];
+    for (const city of this.cities) {
+      if (city !== captured && city.civ === oldCiv) {
+        sources.push({ coords: city.coords, civ: oldCiv });
+      }
+    }
+    for (const source of sources) {
+      const k = key(source.coords.x, source.coords.y);
+      if (visited.has(k)) continue;
+      visited.add(k);
+      claim.set(k, source.civ);
+      frontier.push(source.coords);
+    }
+    while (frontier.length > 0) {
+      const nextFrontier = [];
+      const nextClaim = new Map();
+      for (const coords of frontier) {
+        const civ = claim.get(key(coords.x, coords.y));
+        for (const neighbour of this._neighbours(coords)) {
+          const nk = key(neighbour.x, neighbour.y);
+          if (visited.has(nk) || !this._isLand(neighbour)) continue;
+          if (nextClaim.has(nk)) {
+            if (nextClaim.get(nk) === newCiv && civ === oldCiv) nextClaim.set(nk, oldCiv);
+            continue;
+          }
+          nextClaim.set(nk, civ);
+          nextFrontier.push(neighbour);
+        }
+      }
+      for (const [k, civ] of nextClaim) {
+        claim.set(k, civ);
+        visited.add(k);
+      }
+      frontier = nextFrontier;
+    }
+    return claim;
+  }
+
   _generatePopulation() {
     this.tilePopulation = new Map();
     for (const k in this.tiles) {
@@ -912,6 +1483,7 @@ export class GameState {
       return {
         population: 0, gdp: 0, gdpPerCapita: 0, budget: 0,
         upkeep: 0, research: 0, culture: 0, government: 0,
+        breakdown: null,
       };
     }
     const aggregates = this._playerAggregates(viewerCiv);
@@ -926,6 +1498,7 @@ export class GameState {
       research: this.getResearch(viewerCiv),
       culture: this.getCulture(viewerCiv),
       government: this.getGovernment(viewerCiv),
+      breakdown: this.budgetBreakdown(viewerCiv),
     };
   }
 
@@ -939,6 +1512,7 @@ export class GameState {
       population: city.population,
       improvements: city.improvements,
       buildings: { ...city.buildings },
+      statuses: city.statuses || [],
     }));
   }
 
@@ -962,6 +1536,7 @@ export class GameState {
         coords: [unit.coords.x, unit.coords.y],
         hp: unit.hp,
         maxHp: unit.maxHp,
+        statuses: unit.statuses || [],
         path,
         pathIndex,
         progressHours: unit.progressHours,
diff --git a/shared/hex_pathfinder.js b/shared/hex_pathfinder.js
index eeb2d2b..9eb9139 100644
--- a/shared/hex_pathfinder.js
+++ b/shared/hex_pathfinder.js
@@ -2,12 +2,14 @@
 // the graph with callbacks so the algorithm stays pure and testable:
 //
 //   neighbours(coords) -> [{x,y}, ...]
-//   canEnter(coords) -> bool
+//   canEnter(coords, isGoal) -> bool
 //   stepCost(from, to) -> number
 //   heuristic(from, to) -> number
 //
-// findPath returns the cells from start to goal inclusive, or [] when the goal
-// cannot be entered or is unreachable.
+// canEnter is told whether the tile is the destination, so a caller can allow
+// entering a tile it would otherwise route around (a hostile unit or city) only
+// as the very goal. findPath returns the cells from start to goal inclusive, or
+// [] when the goal cannot be entered or is unreachable.
 
 import { key } from "./hex.js";
 
@@ -69,7 +71,7 @@ export class HexPathfinder {
   findPath(start, goal, neighbours, canEnter, stepCost, heuristic) {
     const startKey = key(start.x, start.y);
     const goalKey = key(goal.x, goal.y);
-    if (startKey === goalKey || !canEnter(goal)) return [];
+    if (startKey === goalKey || !canEnter(goal, true)) return [];
     const open = new MinHeap();
     const cameFrom = new Map();
     const gScore = new Map();
@@ -85,7 +87,7 @@ export class HexPathfinder {
       for (const neighbour of neighbours(current)) {
         const neighbourKey = key(neighbour.x, neighbour.y);
         if (closed.has(neighbourKey)) continue;
-        if (neighbourKey !== goalKey && !canEnter(neighbour)) continue;
+        if (!canEnter(neighbour, neighbourKey === goalKey)) continue;
         const tentative = (gScore.has(currentKey) ? gScore.get(currentKey) : Infinity) +
           stepCost(current, neighbour);
         if (tentative < (gScore.has(neighbourKey) ? gScore.get(neighbourKey) : Infinity)) {
diff --git a/shared/rules.js b/shared/rules.js
index bbbc5fc..9fb948f 100644
--- a/shared/rules.js
+++ b/shared/rules.js
@@ -1,7 +1,7 @@
 // Catalogue maths shared by the server (which charges costs) and the browser
 // (which displays and disables buttons) so the numbers always agree.
 
-import { effectValue } from "./data.js";
+import { effectValue, CITY_DEFENSE_BONUS } from "./data.js";
 
 export function buildingBuildCost(proto, gdp, level) {
   return (proto.baseCost + proto.costGdpFraction * Math.max(gdp, 0)) *
@@ -56,3 +56,29 @@ export function prerequisitesMet(technology, researchedSet, catalogue) {
   }
   return true;
 }
+
+// Every defense modifier of the tile a unit stands on, in display order. The
+// tile carries its own terrain bonus and a city adds another; each entry is a
+// fraction of the unit's base defense. Shared by the server (which fights with
+// them) and the browser (which shows them) so the numbers always agree.
+export function defenseFactors(tile, hasCity) {
+  const factors = [];
+  if (tile && tile.defenseBonus) {
+    factors.push({ label: tile.terrainType, bonus: tile.defenseBonus });
+  }
+  if (hasCity) factors.push({ label: "City", bonus: CITY_DEFENSE_BONUS });
+  return factors;
+}
+
+// Multiplier applied to a unit's base defense for the tile it occupies.
+export function defenseMultiplier(tile, hasCity) {
+  let total = 0;
+  for (const factor of defenseFactors(tile, hasCity)) total += factor.bonus;
+  return 1 + total;
+}
+
+// A unit's defense on a tile, before any role bonus (the attacker/defender
+// distinction is a combat rule, not part of the stat shown to the player).
+export function unitDefense(baseDefense, tile, hasCity) {
+  return baseDefense * defenseMultiplier(tile, hasCity);
+}
diff --git a/tests/data_test.js b/tests/data_test.js
index 557db5b..55fe2c7 100644
--- a/tests/data_test.js
+++ b/tests/data_test.js
@@ -6,7 +6,6 @@ import {
   GOVERNMENTS,
   TECHNOLOGIES,
   TRAINABLE_UNIT_IDS,
-  CITY_DESCRIPTIONS,
   protoUnitById,
   buildingById,
   governmentById,
@@ -47,11 +46,20 @@ export class DataTest extends TestCase {
     }
   }
 
-  test_named_capitals_are_defined_for_france_and_britain() {
-    this.assertNotNull(CITY_DESCRIPTIONS.france);
-    this.assertNotNull(CITY_DESCRIPTIONS.britain);
-    this.assertEqual(CITY_DESCRIPTIONS.france.name, "Paris");
-    this.assertGreater(CITY_DESCRIPTIONS.france.population, 0);
+  test_artillery_is_expensive_slow_and_long_ranged() {
+    const infantry = protoUnitById("modern_infantry");
+    const artillery = protoUnitById("artillery");
+    this.assertNotNull(artillery, "artillery exists");
+    this.assertTrue(artillery.military, "artillery is military");
+    this.assertGreater(artillery.cost, infantry.cost * 2, "much more expensive");
+    this.assertGreater(artillery.upkeep, infantry.upkeep, "costlier to keep");
+    this.assertLess(artillery.speed, infantry.speed, "slower than infantry");
+    this.assertLess(artillery.defense, infantry.defense / 4, "nearly no defense");
+    this.assertGreater(artillery.attack, infantry.attack, "hits harder");
+    this.assertGreater(artillery.range, infantry.range, "outranges infantry");
+    this.assertEqual(artillery.range, 2);
+    this.assertTrue(TRAINABLE_UNIT_IDS.includes("artillery"), "artillery is trainable");
+    this.assertTrue(artillery.icon.endsWith(".svg"));
   }
 
   test_buildings_and_governments_carry_effects() {
diff --git a/tests/framework/helpers.js b/tests/framework/helpers.js
index 70a682b..ce31792 100644
--- a/tests/framework/helpers.js
+++ b/tests/framework/helpers.js
@@ -60,6 +60,7 @@ export function mapLayers($) {
     fog: $("#layer-fog"),
     paths: $("#layer-paths"),
     entities: $("#layer-entities"),
+    labels: $("#layer-labels"),
   };
 }
 
diff --git a/tests/game_screen_test.js b/tests/game_screen_test.js
index 4701abf..617462c 100644
--- a/tests/game_screen_test.js
+++ b/tests/game_screen_test.js
@@ -51,7 +51,8 @@ export class GameScreenTest extends TestCase {
 
       env.$("#city-train").click();
       this.assertFalse(env.$("#modal-train").hasClass("hidden"));
-      env.$("#train-list button").click();
+      this.assertSize(env.$("#train-list button"), 2, "infantry and artillery can be trained");
+      env.$("#train-list button").first().click();
       this.assertEqual(network.orders[0], { type: "train", city: capital.id, proto: 0 });
 
       const unit = state.units.find((u) => u.civ === 0);
@@ -205,8 +206,7 @@ export class GameScreenTest extends TestCase {
     }
   }
 
-  async test_snapshot_refreshes_researched_and_buildings() {
-    const env = await setupDom();
+  async test_snapshot_refreshes_researched_and_buildings() {    const env = await setupDom();
     try {
       const screen = new GameScreen(stubNetwork(), makeConfig());
       screen.enter();
@@ -230,4 +230,71 @@ export class GameScreenTest extends TestCase {
       teardownDom(env);
     }
   }
+
+  async test_unit_panel_shows_terrain_defense_and_tooltip() {
+    const env = await setupDom();
+    try {
+      const screen = new GameScreen(stubNetwork(), makeConfig());
+      screen.enter();
+      const state = defaultState();
+      const mountain = state.landCells.find(
+        (c) => state.tiles[`${c.x},${c.y}`].terrainType === "Mountain"
+      );
+      this.assertNotNull(mountain, "the map has a mountain");
+      const unit = state._spawnUnit(mountain, 0, state.protoUnits[0]);
+      screen.onState(state.snapshot(0));
+      const data = state.snapshot(0).units.find((u) => u.id === unit.id);
+      screen._showUnit(data);
+
+      const proto = screen.protoUnits[unit.proto];
+      this.assertEqual(env.$("#unit-attack").text(), `Attack ${proto.attack}`);
+      this.assertEqual(env.$("#unit-attack").attr("data-tooltip"), `Base ${proto.attack}`);
+      this.assertEqual(env.$("#unit-defense").text(), `Defense ${proto.defense * 2}`);
+      this.assertEqual(
+        env.$("#unit-defense").attr("data-tooltip"),
+        `Base ${proto.defense}, Mountain +${proto.defense}`
+      );
+
+      env.$("#unit-defense").trigger("mouseenter");
+      this.assertFalse(env.$("#stat-tooltip").hasClass("hidden"));
+      this.assertEqual(
+        env.$("#stat-tooltip").text(),
+        `Base ${proto.defense}, Mountain +${proto.defense}`
+      );
+      env.$("#unit-defense").trigger("mouseleave");
+      this.assertTrue(env.$("#stat-tooltip").hasClass("hidden"));
+      screen.leave();
+    } finally {
+      teardownDom(env);
+    }
+  }
+
+  async test_unit_panel_shows_city_defense_bonus() {
+    const env = await setupDom();
+    try {
+      const screen = new GameScreen(stubNetwork(), makeConfig());
+      screen.enter();
+      const state = defaultState();
+      const plain = state.landCells.find(
+        (c) => state.tiles[`${c.x},${c.y}`].terrainType === "Land" &&
+          !state.cityAt(c) && state.topology.neighbours(c.x, c.y).some((n) => state._isLand(n))
+      );
+      this.assertNotNull(plain, "found a plain tile");
+      state._spawnCity({ civIndex: 0, coords: { x: plain.x, y: plain.y }, isCapital: false });
+      state._rebuildCityIndex();
+      const unit = state._spawnUnit(plain, 0, state.protoUnits[0]);
+      screen.onState(state.snapshot(0));
+      screen._showUnit(state.snapshot(0).units.find((u) => u.id === unit.id));
+
+      const proto = screen.protoUnits[unit.proto];
+      this.assertEqual(env.$("#unit-defense").text(), `Defense ${Math.round(proto.defense * 1.5)}`);
+      this.assertEqual(
+        env.$("#unit-defense").attr("data-tooltip"),
+        `Base ${proto.defense}, City +${Math.round(proto.defense * 0.5)}`
+      );
+      screen.leave();
+    } finally {
+      teardownDom(env);
+    }
+  }
 }
diff --git a/tests/game_state_buildings_test.js b/tests/game_state_buildings_test.js
index 7acb831..701903d 100644
--- a/tests/game_state_buildings_test.js
+++ b/tests/game_state_buildings_test.js
@@ -1,6 +1,6 @@
 import { TestCase } from "./framework/test_case.js";
 import { smallState, cityOf, gdpBuilding } from "./framework/helpers.js";
-import { EFFECT_RESEARCH } from "../shared/data.js";
+import { ECONOMY, EFFECT_BUDGET_INCOME, EFFECT_RESEARCH } from "../shared/data.js";
 
 const BIG_BUDGET = 1.0e15;
 
@@ -90,6 +90,46 @@ export class GameStateBuildingsTest extends TestCase {
     this.assertApprox(state.getResearch(0) - first - governmentRate, 2.0);
   }
 
+  test_viewer_stats_split_income_and_upkeep() {
+    const state = smallState();
+    state.budgets.set(0, BIG_BUDGET);
+    const index = this.addBuilding(
+      state,
+      gdpBuilding({ baseCost: 0, costGdpFraction: 0, baseUpkeep: 100, upkeepAlpha: 1.0, effects: [] })
+    );
+    this.assertTrue(state.requestBuild(cityOf(state, 0).id, index));
+    const breakdown = state.viewerStats(0).breakdown;
+    this.assertHas(breakdown, "income");
+    this.assertHas(breakdown, "buildingUpkeep");
+    this.assertHas(breakdown, "unitUpkeep");
+    this.assertApprox(breakdown.buildingUpkeep.total, 100);
+    this.assertApprox(
+      breakdown.unitUpkeep.total,
+      state.getPlayerUpkeep(0) - breakdown.buildingUpkeep.total
+    );
+    const expected = state.getPlayerGdp(0) * ECONOMY.budgetGdpRate * (1 + breakdown.income.modifier);
+    this.assertApprox(breakdown.income.total, expected);
+  }
+
+  test_budget_breakdown_names_income_sources() {
+    const state = smallState();
+    state.budgets.set(0, BIG_BUDGET);
+    const effect = { stat: EFFECT_BUDGET_INCOME, baseValue: 0.05, exponent: 1.0 };
+    const index = this.addBuilding(
+      state,
+      gdpBuilding({ baseCost: 0, costGdpFraction: 0, baseUpkeep: 0, effects: [effect] })
+    );
+    this.assertTrue(state.requestBuild(cityOf(state, 0).id, index));
+    const breakdown = state.viewerStats(0).breakdown;
+    const source = breakdown.income.sources.find((s) => s.label === "Test market");
+    this.assertTrue(source, "the building appears as an income source");
+    this.assertEqual(source.kind, "building");
+    this.assertApprox(source.effect, 0.05);
+    this.assertApprox(breakdown.income.modifier, state.getCivModifiers(0)[EFFECT_BUDGET_INCOME] || 0);
+    this.assertApprox(source.amount, breakdown.income.base * 0.05);
+    this.assertApprox(breakdown.income.total, breakdown.income.base * (1 + breakdown.income.modifier));
+  }
+
   test_snapshot_exposes_buildings_and_resources() {
     const state = smallState();
     const snapshot = state.snapshot(0);
diff --git a/tests/hex_pathfinder_test.js b/tests/hex_pathfinder_test.js
index 3cf4ba7..1f2867e 100644
--- a/tests/hex_pathfinder_test.js
+++ b/tests/hex_pathfinder_test.js
@@ -64,6 +64,22 @@ export class HexPathfinderTest extends TestCase {
     this.assertTrue(isConnected(path));
   }
 
+  test_a_tile_off_limits_for_transit_is_avoided() {
+    const canEnter = (c, isGoal) => !(c.x === 1 && c.y === 0) || isGoal;
+    const path = find({ x: 0, y: 0 }, { x: 2, y: 0 }, canEnter);
+    this.assertTrue(path.length > 3, "the path detours around the blocked tile");
+    for (const cell of path) {
+      this.assertFalse(cell.x === 1 && cell.y === 0, "never steps onto the blocked tile");
+    }
+  }
+
+  test_the_goal_may_be_off_limits_for_transit() {
+    const canEnter = (c, isGoal) => !(c.x === 1 && c.y === 0) || isGoal;
+    const path = find({ x: 0, y: 0 }, { x: 1, y: 0 }, canEnter);
+    this.assertSize(path, 2);
+    this.assertEqual(path[1], { x: 1, y: 0 });
+  }
+
   test_prefers_a_cheaper_detour() {
     // The straight road is expensive; a one-tile detour must be chosen.
     const expensive = new Set(["1,0", "2,0"]);
diff --git a/tests/modals_test.js b/tests/modals_test.js
index d5e5ecf..6ffb390 100644
--- a/tests/modals_test.js
+++ b/tests/modals_test.js
@@ -135,4 +135,58 @@ export class NationModalTest extends TestCase {
       teardownDom(env);
     }
   }
+
+  async test_budget_tab_shows_income_and_upkeep_breakdown() {
+    const env = await setupDom();
+    try {
+      const modal = new NationModal();
+      const finances = {
+        income: {
+          rate: 0.001,
+          base: 900,
+          modifier: 0.15,
+          total: 1035,
+          sources: [
+            { label: "Bank", kind: "building", effect: 0.05, amount: 45 },
+            { label: "Republic", kind: "government", effect: 0.1, amount: 90 },
+          ],
+        },
+        buildingUpkeep: { total: 400, sources: [{ label: "Bank", kind: "building", amount: 400 }] },
+        unitUpkeep: {
+          total: 150,
+          sources: [{ label: "Modern infantry", kind: "unit", amount: 150, count: 3 }],
+        },
+        net: 485,
+      };
+      modal.show(GOVERNMENTS, 0, TECHNOLOGIES, new Set(), 1.0e9, 1.0e15, 1.0e6, finances);
+      env.$("#modal-nation .tab[data-tab=budget]").click();
+      this.assertTrue(env.$("#tab-budget").hasClass("active"));
+
+      const rows = env.$("#budget-list .row-card");
+      this.assertSize(rows, 4);
+      this.assertTrue(rows.eq(0).find(".value").text().includes("+€1 035/h"));
+      this.assertTrue(rows.eq(0).find(".budget-detail").text().includes("Tax rate 0.10% of GDP"));
+      this.assertTrue(rows.eq(0).find(".budget-detail").text().includes("Bank (building) +5.0%"));
+      this.assertTrue(rows.eq(0).find(".budget-detail").text().includes("Republic (government) +10.0%"));
+      this.assertTrue(rows.eq(1).find(".value").text().includes("−€400/h"));
+      this.assertTrue(rows.eq(1).find(".budget-detail").text().includes("Bank — €400/h"));
+      this.assertTrue(rows.eq(2).find(".value").text().includes("−€150/h"));
+      this.assertTrue(rows.eq(2).find(".budget-detail").text().includes("Modern infantry ×3"));
+      this.assertTrue(rows.eq(3).find(".value").text().includes("+€485/h"));
+      this.assertTrue(rows.eq(3).find(".value").hasClass("positive"));
+      this.assertTrue(env.$("#budget-sub").text().includes("Treasury"));
+
+      modal.refresh(0, new Set(), 1.0e9, 1.0e15, 1.0e6, {
+        income: { rate: 0.001, base: 100, modifier: 0, total: 100, sources: [] },
+        buildingUpkeep: { total: 400, sources: [] },
+        unitUpkeep: { total: 150, sources: [] },
+        net: -450,
+      });
+      this.assertTrue(rows.eq(3).find(".value").text().includes("−€450/h"));
+      this.assertTrue(rows.eq(3).find(".value").hasClass("negative"));
+      this.assertTrue(rows.eq(0).find(".budget-detail").text().includes("No bonuses"));
+    } finally {
+      teardownDom(env);
+    }
+  }
 }
diff --git a/tests/rules_test.js b/tests/rules_test.js
index 6e91826..af12851 100644
--- a/tests/rules_test.js
+++ b/tests/rules_test.js
@@ -8,8 +8,19 @@ import {
   governmentEffects,
   technologyEffects,
   prerequisitesMet,
+  defenseFactors,
+  defenseMultiplier,
+  unitDefense,
 } from "../shared/rules.js";
-import { effectValue, GOVERNMENTS, TECHNOLOGIES, EFFECT_GDP, EFFECT_RESEARCH, EFFECT_CULTURE } from "../shared/data.js";
+import {
+  effectValue,
+  GOVERNMENTS,
+  TECHNOLOGIES,
+  TERRAIN_TILES,
+  EFFECT_GDP,
+  EFFECT_RESEARCH,
+  EFFECT_CULTURE,
+} from "../shared/data.js";
 
 function proto(overrides = {}) {
   return {
@@ -118,4 +129,49 @@ export class RulesTest extends TestCase {
     this.assertEmpty(method.prerequisites);
     this.assertTrue(prerequisitesMet(method, new Set(), TECHNOLOGIES));
   }
+
+  test_defense_factors_come_from_the_tile_and_its_city() {
+    const mountain = TERRAIN_TILES.find((t) => t.terrainType === "Mountain");
+    const plains = TERRAIN_TILES.find((t) => t.terrainType === "Land");
+    this.assertSize(defenseFactors(plains, false), 0, "open land defends normally");
+    this.assertSize(defenseFactors(null, false), 0, "no tile, no factor");
+
+    const mountainFactors = defenseFactors(mountain, false);
+    this.assertSize(mountainFactors, 1);
+    this.assertEqual(mountainFactors[0].label, "Mountain");
+    this.assertApprox(mountainFactors[0].bonus, 1.0);
+
+    const cityFactors = defenseFactors(mountain, true);
+    this.assertSize(cityFactors, 2);
+    this.assertEqual(cityFactors[1].label, "City");
+    this.assertApprox(cityFactors[1].bonus, 0.5);
+  }
+
+  test_defense_multiplier_adds_terrain_and_city_bonuses() {
+    const forest = TERRAIN_TILES.find((t) => t.terrainType === "Forest");
+    const mountain = TERRAIN_TILES.find((t) => t.terrainType === "Mountain");
+    const plains = TERRAIN_TILES.find((t) => t.terrainType === "Land");
+    this.assertApprox(defenseMultiplier(plains, false), 1.0);
+    this.assertApprox(defenseMultiplier(forest, false), 1.33);
+    this.assertApprox(defenseMultiplier(mountain, false), 2.0);
+    this.assertApprox(defenseMultiplier(mountain, true), 2.5);
+  }
+
+  test_unit_defense_scales_the_base_stat() {
+    const mountain = TERRAIN_TILES.find((t) => t.terrainType === "Mountain");
+    this.assertApprox(unitDefense(100, mountain, false), 200);
+    this.assertApprox(unitDefense(100, mountain, true), 250);
+    this.assertApprox(unitDefense(100, null, false), 100);
+  }
+
+  test_terrain_defense_bonuses_match_the_spec() {
+    const bonusOf = (type) => {
+      const tile = TERRAIN_TILES.find((t) => t.terrainType === type);
+      return tile ? tile.defenseBonus : 0;
+    };
+    this.assertApprox(bonusOf("Forest"), 0.33);
+    this.assertApprox(bonusOf("Hills"), 0.33);
+    this.assertApprox(bonusOf("Mountain"), 1.0);
+    this.assertApprox(bonusOf("Land"), 0);
+  }
 }
diff --git a/tests/run_tests.js b/tests/run_tests.js
index 01d2623..149a0c9 100644
--- a/tests/run_tests.js
+++ b/tests/run_tests.js
@@ -15,6 +15,8 @@ import { TextFormatTest } from "./text_format_test.js";
 import { GameClockTest } from "./game_clock_test.js";
 import { LoginManagerTest } from "./login_manager_test.js";
 import { RulesTest } from "./rules_test.js";
+import { CombatTest } from "./combat_test.js";
+import { SiegeTest } from "./siege_test.js";
 import { GameStateTest } from "./game_state_test.js";
 import { GameStateBuildingsTest } from "./game_state_buildings_test.js";
 import { GameStateGovernmentTest } from "./game_state_government_test.js";
@@ -41,6 +43,8 @@ const SUITES = [
   GameClockTest,
   LoginManagerTest,
   RulesTest,
+  CombatTest,
+  SiegeTest,
   GameStateTest,
   GameStateBuildingsTest,
   GameStateGovernmentTest,