Add wall art decals to Wolfenstein levels

- Add new `wallArt` level data array with per-cell decal frames
- Integrate wall art rendering into WolfensteinView using same texture sampling as walls
- Add Wall Art tool to WolfensteinEditor with dynamic dropdown from JSON registry
- Create wolfenstein-wallart.json frame registry for easy decal management
- Add validation ensuring wall art sits on actual wall cells
- Support wall art in save/load system with backward compatibility
- Alert idle enemies when shot, even outside vision cone

assets/gamedata/wolfenstein/level-e1m1.json

@@ -512,5 +512,37 @@
     "y": 18.5,
     "radius": 0.6
   },
-  "briefing": []
+  "briefing": [],
+  "wallArt": [
+    {
+      "x": 11,
+      "y": 2,
+      "frame": 0
+    },
+    {
+      "x": 11,
+      "y": 4,
+      "frame": 0
+    },
+    {
+      "x": 11,
+      "y": 6,
+      "frame": 0
+    },
+    {
+      "x": 11,
+      "y": 8,
+      "frame": 0
+    },
+    {
+      "x": 7,
+      "y": 14,
+      "frame": 1
+    },
+    {
+      "x": 1,
+      "y": 15,
+      "frame": 1
+    }
+  ]
 }

data/wolfenstein-artwork.json

@@ -3,7 +3,8 @@
   "sheets": {
     "walls": { "key": "wolfenstein-walls", "path": "assets/images/wolfenstein/walls.png", "frameWidth": 64, "frameHeight": 64 },
     "guard": { "key": "wolfenstein-guard-sheet", "path": "assets/images/wolfenstein/enemies.png", "frameWidth": 128, "frameHeight": 128 },
-    "doors": { "key": "wolfenstein-doors", "path": "assets/images/wolfenstein/doors.png", "frameWidth": 64, "frameHeight": 64 }
+    "doors": { "key": "wolfenstein-doors", "path": "assets/images/wolfenstein/doors.png", "frameWidth": 64, "frameHeight": 64 },
+    "wallArt": { "key": "wolfenstein-wall-art", "path": "assets/images/wolfenstein/wall-art.png", "frameWidth": 64, "frameHeight": 64 }
   },
   "artwork": [
     { "key": "wolfenstein-item-pistol", "path": null },

data/wolfenstein-wallart.json

@@ -0,0 +1,7 @@
+{
+  "_readme": "Frame registry for the wall-art decal sheet (assets/images/wolfenstein/wall-art.png, sheets.wallArt in wolfenstein-artwork.json, 64x64 frames, transparent PNGs painted on top of a wall's own texture). To add a new decal: paint the next 64x64 tile into wall-art.png, then append an entry here — WolfensteinEditor.js's Wall Art dropdown reads this file directly, no code changes needed.",
+  "frames": [
+    { "frame": 0, "id": "nazi-flag", "name": "Nazi Flag" },
+    { "frame": 1, "id": "hitler-pic", "name": "Hitler Pic" }
+  ]
+}

src/games/wolfenstein/WolfensteinEditor.js

@@ -62,6 +62,8 @@ const FACING_DIRS = {
 // null` (just Erase) gets its label alone. The tool id actually used by
 // applyTool()/WALL_TOOLS is either the selected option's id, or — for a
 // dropdown-less category — the category's own id.
+const WALLART_PREFIX = 'wallart:';
+
 const CATEGORIES = [
   { id: 'wall', label: 'Wall', options: [
     { id: 'wall1', label: 'Stone' },
@@ -69,6 +71,13 @@ const CATEGORIES = [
     { id: 'wall3', label: 'Blue' },
     { id: 'wall4', label: 'Green' },
   ] },
+  // Options populated from data/wolfenstein-wallart.json once it loads (see
+  // create()'s fetch + refreshWallArtOptions) — empty here just gives
+  // buildToolPanel a <select> to patch into rather than a hardcoded list,
+  // since new decal frames are meant to be added to that JSON alone, no
+  // code changes. Each option's id is `${WALLART_PREFIX}${frame}` so
+  // applyTool can recover which frame is selected without a second lookup.
+  { id: 'wallart', label: 'Wall Art', options: [] },
   { id: 'door', label: 'Door', options: [
     { id: 'door', label: 'Normal' },
   ] },
@@ -134,6 +143,13 @@ export default class WolfensteinEditor extends Phaser.Scene {
         this.refreshLoadOptions();
       }).catch(() => {});
 
+    this.wallArtFrames = [];
+    fetch('data/wolfenstein-wallart.json').then((r) => r.json())
+      .then((d) => {
+        this.wallArtFrames = d.frames ?? [];
+        this.refreshWallArtOptions();
+      }).catch(() => {});
+
     this.buildToolbar();
     this.buildLoadPanel();
     this.buildMinimap();
@@ -153,7 +169,7 @@ export default class WolfensteinEditor extends Phaser.Scene {
       campaignId: null, missionIndex: 0,
       width: W, height: H, cellSize: 64,
       walls, playerStart: { x: 1.5, y: 1.5, angle: 0 },
-      doors: [], enemies: [], items: [],
+      doors: [], enemies: [], items: [], wallArt: [],
       exit: { x: W - 1.5, y: H - 1.5, radius: 0.6 },
       briefing: [],
     };
@@ -317,6 +333,7 @@ export default class WolfensteinEditor extends Phaser.Scene {
       doors: this.level.doors.filter((d) => d.x < w - 1 && d.y < h - 1),
       enemies: this.level.enemies.filter((e) => e.x < w - 1 && e.y < h - 1),
       items: this.level.items.filter((it) => it.x < w - 1 && it.y < h - 1),
+      wallArt: (this.level.wallArt ?? []).filter((wa) => wa.x < w - 1 && wa.y < h - 1),
       playerStart: this.level.playerStart && this.level.playerStart.x < w - 1 && this.level.playerStart.y < h - 1 ? this.level.playerStart : null,
       exit: this.level.exit && this.level.exit.x < w - 1 && this.level.exit.y < h - 1 ? this.level.exit : null,
     };
@@ -378,6 +395,13 @@ export default class WolfensteinEditor extends Phaser.Scene {
     this.loadSelect.innerHTML = opts;
   }
 
+  /** Patches the Wall Art category's <select> once data/wolfenstein-wallart.json loads — mirrors refreshLoadOptions above. */
+  refreshWallArtOptions() {
+    const select = this.toolPanelDom?.node?.querySelector('select[data-cat="wallart"]');
+    if (!select) return;
+    select.innerHTML = this.wallArtFrames.map((f) => `<option value="${WALLART_PREFIX}${f.frame}">${f.name}</option>`).join('');
+  }
+
   flashLoadWarn(msg) {
     if (!this.loadWarn) return;
     this.loadWarn.textContent = msg;
@@ -404,6 +428,7 @@ export default class WolfensteinEditor extends Phaser.Scene {
       doors: clone.doors ?? [],
       enemies: clone.enemies ?? [],
       items: clone.items ?? [],
+      wallArt: clone.wallArt ?? [],
       playerStart: clone.playerStart ?? null,
       exit: clone.exit ?? null,
     };
@@ -441,7 +466,8 @@ export default class WolfensteinEditor extends Phaser.Scene {
 
     this.add.text(x, y + size + 16,
       'Right-drag or arrows/WASD: pan\nMouse wheel or +/-: zoom\nF or Fit View: whole level\nClick map above: jump there\n\n'
-      + 'Patrol tool: click a guard to\nselect it, then click tiles to\nadd/remove its route nodes.\n2+ nodes auto-closes into a loop',
+      + 'Patrol tool: click a guard to\nselect it, then click tiles to\nadd/remove its route nodes.\n2+ nodes auto-closes into a loop\n\n'
+      + 'Wall Art tool: click an existing\nwall to apply/remove the selected\ndecal (yellow outline = applied).',
       { fontFamily: FONT, fontSize: '13px', color: COLORS.textHex, lineSpacing: 5 });
   }
 
@@ -603,6 +629,7 @@ export default class WolfensteinEditor extends Phaser.Scene {
       doors: lvl.doors.map(shift),
       enemies: lvl.enemies.map(shift),
       items: lvl.items.map(shift),
+      wallArt: (lvl.wallArt ?? []).map(shift),
       playerStart: lvl.playerStart ? shift(lvl.playerStart) : null,
       exit: lvl.exit ? shift(lvl.exit) : null,
     };
@@ -613,11 +640,18 @@ export default class WolfensteinEditor extends Phaser.Scene {
 
   applyTool(x, y) {
     const lvl = this.level;
+    // Repainting a wall's own type/color keeps any wall art on it — the
+    // decal isn't tied to a specific wall type, only to the cell being a
+    // wall at all — so this is the one wall-touching branch that does NOT
+    // clear wall art (contrast erase and every floor-placing tool below,
+    // which all turn the cell into non-wall and so must clear it).
     if (WALL_TOOLS[this.tool]) { lvl.walls[y][x] = WALL_TOOLS[this.tool]; this.clearEntitiesAt(x, y); return; }
-    if (this.tool === 'erase') { lvl.walls[y][x] = 0; this.clearEntitiesAt(x, y); return; }
+    if (this.tool === 'erase') { lvl.walls[y][x] = 0; this.clearEntitiesAt(x, y); this.clearWallArtAt(x, y); return; }
     if (this.tool === 'patrol') { this.applyPatrolTool(x, y); return; }
+    if (this.tool.startsWith(WALLART_PREFIX)) { this.applyWallArtTool(x, y, Number(this.tool.slice(WALLART_PREFIX.length))); return; }
 
     lvl.walls[y][x] = 0; // every remaining tool places on floor
+    this.clearWallArtAt(x, y);
     if (this.tool === 'door') {
       const i = lvl.doors.findIndex((d) => d.x === x && d.y === y);
       if (i >= 0) lvl.doors.splice(i, 1); else lvl.doors.push({ x, y, orientation: 'vertical' });
@@ -667,6 +701,29 @@ export default class WolfensteinEditor extends Phaser.Scene {
     if (i >= 0) enemy.patrol.splice(i, 1); else enemy.patrol.push({ x: x + 0.5, y: y + 0.5 });
   }
 
+  /**
+   * Wall Art: only an actual wall cell (walls[y][x] > 0 — floor, and door
+   * cells too since a door leaves walls[y][x] at 0 in editor-authored level
+   * JSON, both fail this check the same way) is a valid decal surface.
+   * Clicking one with no art applies the selected frame; clicking one that
+   * already has art removes it — a straight toggle, regardless of which
+   * frame is currently selected in the dropdown, so switching an
+   * already-decorated wall from one decal to another is two clicks
+   * (remove, then apply) rather than an implicit replace.
+   */
+  applyWallArtTool(x, y, frame) {
+    const lvl = this.level;
+    if (!(lvl.walls[y]?.[x] > 0)) return;
+    lvl.wallArt = lvl.wallArt ?? [];
+    const i = lvl.wallArt.findIndex((w) => w.x === x && w.y === y);
+    if (i >= 0) lvl.wallArt.splice(i, 1); else lvl.wallArt.push({ x, y, frame });
+  }
+
+  clearWallArtAt(x, y) {
+    const lvl = this.level;
+    lvl.wallArt = (lvl.wallArt ?? []).filter((w) => !(w.x === x && w.y === y));
+  }
+
   clearEntitiesAt(x, y) {
     const lvl = this.level;
     const removedEnemy = lvl.enemies.find((e) => Math.floor(e.x) === x && Math.floor(e.y) === y);
@@ -766,6 +823,16 @@ export default class WolfensteinEditor extends Phaser.Scene {
     g.fillStyle(0xb08040, 1);
     for (const d of lvl.doors) { const [bx, by] = this.toBoard(d.x, d.y); g.fillRect(bx, by, k - 1, k - 1); }
 
+    // Decorated walls get a yellow outline at all times (not just while the
+    // Wall Art tool is active) — same "always visible, not tool-scoped"
+    // treatment as doors above, since it's level content worth seeing no
+    // matter which tool you're currently using.
+    g.lineStyle(2, 0xffe066, 1);
+    for (const w of lvl.wallArt ?? []) {
+      const [bx, by] = this.toBoard(w.x, w.y);
+      g.strokeRect(bx + 1, by + 1, k - 3, k - 3);
+    }
+
     if (lvl.playerStart) {
       const [bx, by] = this.toBoard(lvl.playerStart.x, lvl.playerStart.y);
       g.fillStyle(0x38b048, 1); g.fillCircle(bx, by, k * 0.35);

src/games/wolfenstein/WolfensteinLogic.js

@@ -57,9 +57,15 @@ export function createState(level, rules) {
   const cooldowns = {};
   for (const w of rules.weapons) cooldowns[w.id] = 0;
 
+  // Wall art (decal painted on top of a wall's own texture) is static,
+  // level-authored decoration with no runtime behavior of its own — it just
+  // rides along on state.map for WolfensteinView to sample, the same way
+  // the wall grid itself does.
+  const wallArt = (level.wallArt ?? []).map((w) => ({ x: w.x, y: w.y, frame: w.frame }));
+
   return {
     tick: 0, accumulatorMs: 0, alpha: 0,
-    map: { width: level.width, height: level.height, walls },
+    map: { width: level.width, height: level.height, walls, wallArt },
     player: {
       x: level.playerStart.x, y: level.playerStart.y,
       angle: ((level.playerStart.angle ?? 0) * Math.PI) / 180,
@@ -573,11 +579,21 @@ function stepProjectiles(state, rules) {
         const dmg = rollDamage(rules.ammoTypeById[proj.ammoType]);
         if (proj.friendly) {
           // Ammo hitting an enemy both damages and stuns it (unless the
-          // hit was lethal — a dead enemy has nothing left to flinch).
+          // hit was lethal — a dead enemy has nothing left to flinch). Being
+          // shot is also unconditional proof of the player's presence — it
+          // alerts the enemy the same way spotting the player or hearing
+          // gunfire in its room does, regardless of range/LOS/facing-cone
+          // (a shot from outside its own vision cone, e.g. from behind,
+          // still counts). Only a genuinely idle enemy transitions here;
+          // one already alert/chasing/attacking has nothing to escalate.
           damageEnemy(state, bestTarget, dmg);
           if (!bestTarget.dead) {
             bestTarget.stunMs = rules.enemyById[bestTarget.defId].stunMs ?? 0;
             state.events.push({ t: 'enemyStunned', id: bestTarget.id });
+            if (bestTarget.state === 'idle') {
+              bestTarget.state = 'alert';
+              state.events.push({ t: 'enemyAlert', id: bestTarget.id });
+            }
           }
         } else {
           applyDamageToPlayer(state, dmg);
@@ -647,6 +663,7 @@ export function buildLevelModel(levelJson) {
     doors: (levelJson.doors ?? []).map((d) => ({ ...d })),
     enemies: (levelJson.enemies ?? []).map((e) => ({ ...e })),
     items: (levelJson.items ?? []).map((it) => ({ ...it })),
+    wallArt: (levelJson.wallArt ?? []).map((w) => ({ ...w })),
     exit: levelJson.exit ? { ...levelJson.exit } : null,
     briefing: (levelJson.briefing ?? []).slice(),
   };
@@ -717,6 +734,9 @@ export function validateLevel(level) {
     const c = { x: Math.floor(it.x), y: Math.floor(it.y) };
     if (level.walls[c.y]?.[c.x] > 0) issues.push(`item (${it.x},${it.y}) sits inside a wall cell`);
   }
+  for (const w of level.wallArt ?? []) {
+    if (!(level.walls[w.y]?.[w.x] > 0)) issues.push(`wall art (${w.x},${w.y}) does not sit on a wall cell`);
+  }
 
   const reachable = bfsReachable(level, startCell, exitCell);
   if (!reachable) issues.push('exit is not reachable from playerStart');
@@ -755,7 +775,7 @@ export function serialize(state) {
   return JSON.stringify({
     v: SAVE_VERSION,
     tick: state.tick, accumulatorMs: state.accumulatorMs,
-    map: { width: state.map.width, height: state.map.height, wallsRle: rleEncodeGrid(state.map.walls) },
+    map: { width: state.map.width, height: state.map.height, wallsRle: rleEncodeGrid(state.map.walls), wallArt: state.map.wallArt },
     player: { ...state.player, weapons: state.player.weapons.slice(), ammo: { ...state.player.ammo } },
     enemies: state.enemies.map((e) => ({ ...e })),
     projectiles: state.projectiles.map((p) => ({ ...p })),
@@ -773,7 +793,14 @@ export function deserialize(rules, raw) {
   if (!data || data.v !== SAVE_VERSION) return null;
   return {
     tick: data.tick, accumulatorMs: data.accumulatorMs, alpha: 0,
-    map: { width: data.map.width, height: data.map.height, walls: rleDecodeGrid(data.map.wallsRle, data.map.width, data.map.height) },
+    // wallArt defaults to [] for a save taken before this feature existed —
+    // purely cosmetic, static data, so a missing field degrades to "no
+    // decals" instead of needing a SAVE_VERSION bump.
+    map: {
+      width: data.map.width, height: data.map.height,
+      walls: rleDecodeGrid(data.map.wallsRle, data.map.width, data.map.height),
+      wallArt: data.map.wallArt ?? [],
+    },
     player: { ...data.player, ammo: { ...data.player.ammo }, weapons: data.player.weapons.slice(), pendingTurn: 0, fireHeld: false, prevFireHeld: false },
     enemies: data.enemies.map((e) => ({ ...e })),
     projectiles: data.projectiles.map((p) => ({ ...p })),

src/games/wolfenstein/WolfensteinView.js

@@ -96,6 +96,8 @@ export default class WolfensteinView {
 
     this.wallTexture = scene.textures.exists('wolfenstein-walls')
       ? scene.textures.get('wolfenstein-walls') : null;
+    this.wallArtTexture = scene.textures.exists('wolfenstein-wall-art')
+      ? scene.textures.get('wolfenstein-wall-art') : null;
     this.doorTexture = scene.textures.exists('wolfenstein-doors')
       ? scene.textures.get('wolfenstein-doors') : null;
     this.guardTexture = scene.textures.exists('wolfenstein-guard-sheet')
@@ -134,6 +136,11 @@ export default class WolfensteinView {
     ctx.fillStyle = '#4a4a4a';
     ctx.fillRect(0, VIEW_H / 2, VIEW_W, VIEW_H / 2);
 
+    // x,y -> wall-art frame index. map.wallArt is small, level-authored,
+    // static data — cheap enough to rebuild this lookup every call rather
+    // than caching it across frames.
+    const wallArtByCell = new Map((map.wallArt ?? []).map((w) => [`${w.x},${w.y}`, w.frame]));
+
     const cols = castColumns(map, camera, NUM_COLUMNS, doors);
     for (let i = 0; i < NUM_COLUMNS; i++) {
       const hit = cols[i];
@@ -155,26 +162,43 @@ export default class WolfensteinView {
         continue;
       }
 
+      // rawStart/rawEnd (not drawStart/drawEnd) are the true, unclipped
+      // extent of this column — up close that's far taller than the screen.
+      // Crop the source by the same fraction that got clipped off the
+      // destination so the vertical zoom keeps pace with the horizontal one
+      // instead of freezing once the wall overflows VIEW_H. Wall art below
+      // reuses this exact same fraction so a decal lines up pixel-for-pixel
+      // with the wall face beneath it at any distance.
       const frame = this.wallTexture?.frames[WALL_FRAME[hit.wallType]];
       if (frame) {
         const srcX = frame.cutX + Math.min(frame.width - 1, Math.floor(hit.textureX * frame.width));
-        // rawStart/rawEnd (not drawStart/drawEnd) are the true, unclipped
-        // extent of this column — up close that's far taller than the
-        // screen. Crop the source by the same fraction that got clipped off
-        // the destination so the vertical zoom keeps pace with the
-        // horizontal one instead of freezing once the wall overflows VIEW_H.
         const srcY = frame.cutY + ((drawStart - rawStart) / lineHeight) * frame.height;
         const srcH = ((drawEnd - drawStart) / lineHeight) * frame.height;
         ctx.drawImage(frame.source.image, srcX, srcY, 1, srcH, x, y, w, h);
-        ctx.globalCompositeOperation = 'multiply';
-        ctx.fillStyle = shadeGrey(hit);
-        ctx.fillRect(x, y, w, h);
-        ctx.globalCompositeOperation = 'source-over';
       } else {
-        const base = WALL_COLORS[hit.wallType] ?? 0xaaaaaa;
+        ctx.fillStyle = `#${(WALL_COLORS[hit.wallType] ?? 0xaaaaaa).toString(16).padStart(6, '0')}`;
-        ctx.fillStyle = shadeColor(base, hit);
         ctx.fillRect(x, y, w, h);
       }
+
+      // Wall art: an optional decal painted on top of the wall's own
+      // texture (a poster/flag, not a different wall type), sampled with
+      // the identical per-column source-texel technique above so it lines
+      // up with the wall face beneath it, drawn BEFORE the shading pass
+      // below so it darkens with distance/side the same as the wall does —
+      // otherwise it'd read as a flat unlit sticker glued onto a dim wall.
+      const artFrameIndex = wallArtByCell.get(`${hit.mapX},${hit.mapY}`);
+      const artFrame = artFrameIndex != null ? this.wallArtTexture?.frames[artFrameIndex] : null;
+      if (artFrame) {
+        const artSrcX = artFrame.cutX + Math.min(artFrame.width - 1, Math.floor(hit.textureX * artFrame.width));
+        const artSrcY = artFrame.cutY + ((drawStart - rawStart) / lineHeight) * artFrame.height;
+        const artSrcH = ((drawEnd - drawStart) / lineHeight) * artFrame.height;
+        ctx.drawImage(artFrame.source.image, artSrcX, artSrcY, 1, artSrcH, x, y, w, h);
+      }
+
+      ctx.globalCompositeOperation = 'multiply';
+      ctx.fillStyle = shadeGrey(hit);
+      ctx.fillRect(x, y, w, h);
+      ctx.globalCompositeOperation = 'source-over';
     }
     this.canvasTexture.refresh();
   }

src/games/wolfenstein/sprites.md

@@ -15,6 +15,52 @@ order: frame 0 = type 1 (stone), frame 1 = type 2 (wood), frame 2 = type 3
 (blue-tile), frame 3 = type 4 (green-tile). Doors (`DOOR_WALL_TYPE`, type 9)
 are **not** part of this sheet at all — see `sheets.doors` below.
 
+## Wall art decals — `sheets.wallArt`
+
+`frameWidth: 64, frameHeight: 64`, same spritesheet convention as walls —
+but unlike walls/doors this isn't a wall *type*, it's an optional decal
+(poster/flag/etc.) painted on top of whichever wall type is already there.
+**Wired up 2026-08-22.** Painted sheet is `assets/images/wolfenstein/wall-art.png`
+(currently 512×512, an 8×8 grid = 64 frames of headroom; only frames 0-1 are
+assigned so far). Frame *names* (not just indices) live in a separate JSON
+registry, `data/wolfenstein-wallart.json` — `{ frames: [{ frame, id, name }] }`
+— read directly by `WolfensteinEditor.js`'s Wall Art tool dropdown at
+startup (`fetch('data/wolfenstein-wallart.json')`, see `refreshWallArtOptions`).
+To add a new decal: paint the next tile into `wall-art.png`, append one
+entry to that registry — no code changes needed on either side. Current
+frames: `0` = Nazi Flag, `1` = Hitler Pic.
+
+Level data: `level.wallArt: [{ x, y, frame }]`, a sparse per-cell list (like
+`doors`/`items`, not a dense grid) — one entry per decorated wall cell,
+folded into `buildLevelModel`/`validateLevel` in `WolfensteinLogic.js` (an
+entry must sit on an actual wall cell, `walls[y][x] > 0`) and carried
+statically on `state.map.wallArt` (round-trips through save/load; a save
+predating this feature just deserializes to `[]`, no `SAVE_VERSION` bump
+needed since it's purely cosmetic data with no simulation behavior).
+
+Rendering (`WolfensteinView._drawWalls`): sampled with the *exact same*
+per-column source-texel technique as the wall texture itself (same `srcX`
+from `hit.textureX`, same vertical crop math), so a decal lines up
+pixel-for-pixel with the wall face beneath it at any distance — it's drawn
+directly on top of the base wall draw, before the shared `multiply` shading
+pass, so it darkens with distance/side exactly like the wall instead of
+reading as a flat unlit sticker. Falls back to showing nothing (just the
+plain wall) if the sheet isn't loaded — there's no procedural placeholder
+for wall art, unlike walls/doors/guard.
+
+Editor (`WolfensteinEditor.js`): a "Wall Art" tool category whose dropdown
+is the one populated dynamically (from the JSON registry above) rather than
+hardcoded in `CATEGORIES` — every other category's options are static.
+Clicking an existing wall cell with a frame selected toggles that cell's
+entry in `level.wallArt` (apply if absent, remove if present, regardless of
+which frame is currently selected — switching an already-decorated wall to
+a different decal is two clicks). Repainting a wall's type/color keeps its
+wall art (`applyTool`'s `WALL_TOOLS` branch); erasing a wall or placing
+anything that turns the cell to floor clears it (`clearWallArtAt`, called
+alongside every floor-creating branch). Decorated walls get a persistent
+yellow outline on the board regardless of which tool is active, the same
+"always visible" treatment doors get.
+
 ## Door textures — `sheets.doors`
 
 `frameWidth: 64, frameHeight: 64`, same spritesheet convention as walls.