feat: bidirectional door system + editor bi-link tool

Replace spawn-based map transitions with explicit bidirectional door
links. Every exit now requires targetX/targetY — spawn is only used
for initial game start. Remove returnPoints stack from worldState.

Editor improvements:
- New "Bi-Link" tool creates paired exits on both maps at once
- Exit list shows target coordinates and warns if missing
- Canvas renders target info labels below exit tiles
- Properties panel handles game ID ↔ editor ID mapping

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

editor.html

@@ -91,7 +91,8 @@ body { background: var(--bg); color: var(--text); font-family: 'Segoe UI', syste
         <button class="tool-btn" data-tool="erase" title="Click/drag to erase walls">🧹 Erase</button>
         <button class="tool-btn" data-tool="spawn" title="Click to set player spawn">🏠 Spawn</button>
         <button class="tool-btn" data-tool="npc" title="Click to place NPC">👤 NPC</button>
-        <button class="tool-btn" data-tool="exit" title="Click to place exit">🚪 Exit</button>
+        <button class="tool-btn" data-tool="exit" title="Click to place exit (one-way)">🚪 Exit</button>
+        <button class="tool-btn" data-tool="bilink" title="Click to create bidirectional door link" style="background:rgba(0,200,100,0.15)">🔗 Bi-Link</button>
         <button class="tool-btn" data-tool="interaction" title="Click to place interaction">⚡ Interact</button>
         <button class="tool-btn" data-tool="select" title="Click entity to select/move">🔍 Select</button>
         <button class="tool-btn danger" data-tool="delete" title="Click entity to delete">✕ Delete</button>
@@ -144,6 +145,31 @@ body { background: var(--bg); color: var(--text); font-family: 'Segoe UI', syste
     </div>
 </div>
 
+<!-- Bi-Link modal -->
+<div class="modal-overlay" id="bilink-modal">
+    <div class="modal">
+        <h2>🔗 Create Bidirectional Door Link</h2>
+        <p style="color:var(--text2);font-size:12px;margin-bottom:12px;">
+            This creates an exit on the current map AND the matching return exit on the target map.
+        </p>
+        <div id="bilink-form" style="display:flex;flex-direction:column;gap:8px;">
+            <div class="prop-row"><label>From tile</label><span id="bilink-from" style="color:var(--accent);font-family:monospace;"></span></div>
+            <div class="prop-row"><label>Target Map</label><select id="bilink-target-map" style="flex:1;background:var(--bg);color:var(--text);border:1px solid var(--border);border-radius:3px;padding:4px 6px;"></select></div>
+            <div class="prop-row"><label>Enter at X</label><input type="number" id="bilink-enter-x" value="0" style="width:60px;background:var(--bg);color:var(--text);border:1px solid var(--border);border-radius:3px;padding:4px 6px;"></div>
+            <div class="prop-row"><label>Enter at Y</label><input type="number" id="bilink-enter-y" value="0" style="width:60px;background:var(--bg);color:var(--text);border:1px solid var(--border);border-radius:3px;padding:4px 6px;"></div>
+            <hr style="border-color:var(--border);margin:4px 0;">
+            <p style="color:var(--text2);font-size:11px;">Return exit on target map (where the player exits back to this map):</p>
+            <div class="prop-row"><label>Exit tile X</label><input type="number" id="bilink-return-x" value="0" style="width:60px;background:var(--bg);color:var(--text);border:1px solid var(--border);border-radius:3px;padding:4px 6px;"></div>
+            <div class="prop-row"><label>Exit tile Y</label><input type="number" id="bilink-return-y" value="0" style="width:60px;background:var(--bg);color:var(--text);border:1px solid var(--border);border-radius:3px;padding:4px 6px;"></div>
+            <div class="prop-row"><label>Return to X</label><span id="bilink-return-to" style="color:var(--accent);font-family:monospace;"></span></div>
+        </div>
+        <div class="modal-actions">
+            <button onclick="closeModal('bilink-modal')">Cancel</button>
+            <button class="primary" id="btn-do-bilink">🔗 Create Link</button>
+        </div>
+    </div>
+</div>
+
 <!-- Import modal -->
 <div class="modal-overlay" id="import-modal">
     <div class="modal">
@@ -240,6 +266,7 @@ function init() {
     document.getElementById('btn-copy-export').addEventListener('click', copyExport);
     document.getElementById('btn-save-server').addEventListener('click', saveToServer);
     document.getElementById('btn-load-server').addEventListener('click', loadFromServer);
+    document.getElementById('btn-do-bilink').addEventListener('click', createBiLink);
 
     resizeCanvas();
     updateEntityList();
@@ -403,12 +430,29 @@ function render() {
 
     // Exits
     md.exits.forEach((e, i) => {
+        const isSel = selectedEntity?.type === 'exit' && selectedEntity.index === i;
         ctx.fillStyle = 'rgba(50, 255, 50, 0.35)';
         ctx.fillRect(e.x * TILE_PX, e.y * TILE_PX, TILE_PX, TILE_PX);
-        ctx.strokeStyle = selectedEntity?.type === 'exit' && selectedEntity.index === i ? '#fff' : '#55ff55';
-        ctx.lineWidth = selectedEntity?.type === 'exit' && selectedEntity.index === i ? 2.5 : 1.5;
+        ctx.strokeStyle = isSel ? '#fff' : '#55ff55';
+        ctx.lineWidth = isSel ? 2.5 : 1.5;
         ctx.strokeRect(e.x * TILE_PX, e.y * TILE_PX, TILE_PX, TILE_PX);
         drawLabel(ctx, '🚪', e.x, e.y);
+        // Show target info label below the tile
+        if (scale >= 2) {
+            const label = `→${e.targetMap}(${e.targetX ?? '?'},${e.targetY ?? '?'})`;
+            ctx.save();
+            ctx.font = `bold ${Math.max(8, scale * 2.5)}px monospace`;
+            ctx.textAlign = 'center';
+            ctx.textBaseline = 'top';
+            ctx.fillStyle = 'rgba(0,0,0,0.7)';
+            const tw = ctx.measureText(label).width + 4;
+            const lx = e.x * TILE_PX + TILE_PX / 2;
+            const ly = (e.y + 1) * TILE_PX + 1;
+            ctx.fillRect(lx - tw / 2, ly, tw, scale * 3 + 2);
+            ctx.fillStyle = '#55ff55';
+            ctx.fillText(label, lx, ly + 1);
+            ctx.restore();
+        }
     });
 
     // Interactions
@@ -512,11 +556,20 @@ function onMouseDown(e) {
             selectedEntity = { type: 'npc', index: md.npcs.length - 1 };
             updateEntityList(); updateProps(); render();
             break;
-        case 'exit':
-            md.exits.push({ x: tile.x, y: tile.y, targetMap: 'lab', targetX: 0, targetY: 0 });
+        case 'exit': {
+            // Default to a different map than the current one
+            const otherMaps = Object.keys(mapConfigs).filter(id => id !== currentMapId);
+            const defaultTarget = otherMaps[0] || currentMapId;
+            md.exits.push({ x: tile.x, y: tile.y, targetMap: defaultTarget, targetX: 0, targetY: 0 });
             selectedEntity = { type: 'exit', index: md.exits.length - 1 };
             updateEntityList(); updateProps(); render();
             break;
+        }
+        case 'bilink': {
+            // Open bidirectional link dialog
+            openBiLinkDialog(tile.x, tile.y);
+            break;
+        }
         case 'interaction':
             md.interactions.push({ x: tile.x, y: tile.y, type: 'sign', label: 'Sign', dialog: ['...'] });
             selectedEntity = { type: 'interaction', index: md.interactions.length - 1 };
@@ -546,7 +599,7 @@ function onMouseMove(e) {
     if (md.walls.has(key)) info += 'Wall ';
     if (md.spawn.x === tile.x && md.spawn.y === tile.y) info += 'Spawn ';
     md.npcs.forEach(n => { if (n.x === tile.x && n.y === tile.y) info += `NPC:${n.id} `; });
-    md.exits.forEach(e => { if (e.x === tile.x && e.y === tile.y) info += `Exit→${e.targetMap} `; });
+    md.exits.forEach(e => { if (e.x === tile.x && e.y === tile.y) info += `Exit→${e.targetMap}(${e.targetX ?? '?'},${e.targetY ?? '?'}) `; });
     md.interactions.forEach(i => { if (i.x === tile.x && i.y === tile.y) info += `${i.type}:${i.label} `; });
     document.getElementById('tile-info').textContent = info || '(empty)';
 
@@ -704,9 +757,12 @@ function updateEntityList() {
         makeEntityItem('npc', i, '👤', n.id, n.x, n.y, '#cc55ff')
     ).join('') || '<div style="padding:4px 16px;color:var(--text2);font-size:11px;">None</div>';
 
-    document.getElementById('exit-list').innerHTML = md.exits.map((e, i) =>
-        makeEntityItem('exit', i, '🚪', `→ ${e.targetMap}`, e.x, e.y, '#55ff55')
-    ).join('') || '<div style="padding:4px 16px;color:var(--text2);font-size:11px;">None</div>';
+    document.getElementById('exit-list').innerHTML = md.exits.map((e, i) => {
+        const hasCoords = e.targetX != null && e.targetY != null;
+        const coordStr = hasCoords ? `(${e.targetX},${e.targetY})` : '⚠️ NO COORDS';
+        const color = hasCoords ? '#55ff55' : '#ff5555';
+        return makeEntityItem('exit', i, '🚪', `→ ${e.targetMap} ${coordStr}`, e.x, e.y, color);
+    }).join('') || '<div style="padding:4px 16px;color:var(--text2);font-size:11px;">None</div>';
 
     document.getElementById('interaction-list').innerHTML = md.interactions.map((inter, i) =>
         makeEntityItem('interaction', i, '⚡', `${inter.type}: ${inter.label}`, inter.x, inter.y, '#ffdd44')
@@ -771,9 +827,17 @@ function updateProps() {
         html += propSelect('Facing', 'facing', ent.facing, ['down','up','left','right']);
         html += propTextarea('Dialog', 'dialog', (ent.dialog || []).join('\n'));
     } else if (t === 'exit') {
-        html += propSelect('Target Map', 'targetMap', ent.targetMap, Object.keys(mapConfigs));
-        html += propNum('Target X', 'targetX', ent.targetX);
-        html += propNum('Target Y', 'targetY', ent.targetY);
+        // Show map options with both editor ID and game ID
+        const mapOptions = Object.keys(mapConfigs);
+        // Handle game IDs like 'town' being stored as 'pallet-town' internally
+        const currentTarget = ent.targetMap === 'town' ? 'pallet-town' : ent.targetMap;
+        html += propSelect('Target Map', 'targetMap', currentTarget, mapOptions);
+        html += propNum('Target X', 'targetX', ent.targetX ?? 0);
+        html += propNum('Target Y', 'targetY', ent.targetY ?? 0);
+        // Warning if no target coords set
+        if (ent.targetX == null || ent.targetY == null) {
+            html += '<div style="color:var(--red);font-size:10px;padding:2px 0;">⚠️ Set target X/Y! Every exit needs explicit coordinates.</div>';
+        }
     } else if (t === 'interaction') {
         html += propSelect('Type', 'type', ent.type, ['sign','workshop','puzzle_door','terminal','door']);
         html += propText('Label', 'label', ent.label || '');
@@ -818,6 +882,9 @@ function applyPropChange(prop, value, inputType) {
         ent.dialog = value.split('\n').filter(l => l.trim());
     } else if (prop === 'requiredOutputs') {
         ent.requiredOutputs = value.split(',').map(Number);
+    } else if (prop === 'targetMap') {
+        // Store as game ID (pallet-town → town)
+        ent.targetMap = value === 'pallet-town' ? 'town' : value;
     } else if (inputType === 'number' || prop === 'x' || prop === 'y' || prop === 'targetX' || prop === 'targetY') {
         ent[prop] = parseInt(value) || 0;
     } else {
@@ -1126,6 +1193,88 @@ function parseAndLoadMapsJS(src) {
     }
 }
 
+// ==================== Bidirectional Link ====================
+
+let bilinkSourceTile = null;
+
+function openBiLinkDialog(tx, ty) {
+    bilinkSourceTile = { x: tx, y: ty };
+
+    // Populate target map dropdown (exclude current map)
+    const sel = document.getElementById('bilink-target-map');
+    sel.innerHTML = '';
+    for (const [id, cfg] of Object.entries(mapConfigs)) {
+        if (id === currentMapId) continue;
+        const opt = document.createElement('option');
+        opt.value = id;
+        opt.textContent = `${cfg.name} (${id})`;
+        sel.appendChild(opt);
+    }
+
+    document.getElementById('bilink-from').textContent = `(${tx}, ${ty}) on ${mapConfigs[currentMapId].name}`;
+
+    // Smart defaults: return tile = one tile below the source (in front of the door)
+    const returnX = tx;
+    const returnY = Math.min(ty + 1, mapConfigs[currentMapId].heightTiles - 1);
+    document.getElementById('bilink-return-to').textContent = `(${returnX}, ${returnY})`;
+
+    // Update return-to display when source changes
+    document.getElementById('bilink-enter-x').value = 0;
+    document.getElementById('bilink-enter-y').value = 0;
+    document.getElementById('bilink-return-x').value = 0;
+    document.getElementById('bilink-return-y').value = 0;
+
+    openModal('bilink-modal');
+}
+
+// btn-do-bilink wired after init below
+
+function createBiLink() {
+    if (!bilinkSourceTile) return;
+
+    const targetMapId = document.getElementById('bilink-target-map').value;
+    const enterX = parseInt(document.getElementById('bilink-enter-x').value) || 0;
+    const enterY = parseInt(document.getElementById('bilink-enter-y').value) || 0;
+    const returnExitX = parseInt(document.getElementById('bilink-return-x').value) || 0;
+    const returnExitY = parseInt(document.getElementById('bilink-return-y').value) || 0;
+
+    // Return to one tile below the source door (in front of it)
+    const returnToX = bilinkSourceTile.x;
+    const returnToY = Math.min(bilinkSourceTile.y + 1, mapConfigs[currentMapId].heightTiles - 1);
+
+    // Game IDs: pallet-town → town
+    const toGameId = (id) => id === 'pallet-town' ? 'town' : id;
+
+    // 1. Create exit on current map: door → target interior
+    const currentMd = mapData[currentMapId];
+    currentMd.exits.push({
+        x: bilinkSourceTile.x,
+        y: bilinkSourceTile.y,
+        targetMap: toGameId(targetMapId),
+        targetX: enterX,
+        targetY: enterY
+    });
+
+    // 2. Create matching return exit on target map: interior exit → back to this door
+    const targetMd = mapData[targetMapId];
+    if (targetMd) {
+        targetMd.exits.push({
+            x: returnExitX,
+            y: returnExitY,
+            targetMap: toGameId(currentMapId),
+            targetX: returnToX,
+            targetY: returnToY
+        });
+        toast(`Bidirectional link created: ${currentMapId} ↔ ${targetMapId}`);
+    } else {
+        toast(`Exit created on ${currentMapId} (target map ${targetMapId} not loaded)`);
+    }
+
+    closeModal('bilink-modal');
+    selectedEntity = { type: 'exit', index: currentMd.exits.length - 1 };
+    updateEntityList(); updateProps(); render();
+}
+
 // ==================== Boot ====================
 
 init();

js/world/gameMode.js

@@ -1,5 +1,5 @@
 // gameMode.js - Central coordinator: switches between World and Workshop modes
-import { worldState, setPlayerPosition, warpToMap, solvePuzzle, isPuzzleSolved } from './worldState.js';
+import { worldState, setPlayerPosition, warpToMap, isPuzzleSolved } from './worldState.js';
 import { initWorldRenderer, startWorldLoop, stopWorldLoop } from './worldRenderer.js';
 import { initWorldInput, destroyWorldInput, setInteractionHandler } from './worldInput.js';
 import { getMap } from './maps.js';
@@ -112,39 +112,11 @@ function handleInteraction(event) {
         }
 
         case 'mapExit': {
+            // Every exit MUST have targetX/targetY — bidirectional door links.
+            // No spawn fallback. Spawn is only for the initial game start.
             const { targetMap, targetX, targetY } = event.data;
-            const p = worldState.player;
-
-            // Save return point: where the player is NOW (one tile back from the exit)
-            // so when they leave the target map, they return here
-            worldState.returnPoints.push({
-                fromMap: worldState.currentMap,
-                fromX: p.x,
-                fromY: p.y
-            });
-
-            // If exit has explicit coordinates, use them
-            // Otherwise, check for a stored return point for the target map
-            if (targetX != null && targetY != null) {
-                warpToMap(targetMap, targetX, targetY);
-            } else {
-                // Pop the most recent return point for this map
-                const retIdx = worldState.returnPoints.findLastIndex(
-                    rp => rp.fromMap === targetMap
-                );
-                if (retIdx >= 0) {
-                    const ret = worldState.returnPoints[retIdx];
-                    worldState.returnPoints.splice(retIdx, 1);
-                    warpToMap(ret.fromMap, ret.fromX, ret.fromY);
-                } else {
-                    // Fallback: use map spawn point
-                    const destMap = getMap(targetMap);
-                    const sx = destMap?.spawn?.x ?? 0;
-                    const sy = destMap?.spawn?.y ?? 0;
-                    warpToMap(targetMap, sx, sy);
-                }
-            }
-            console.log(`[gameMode] warped to ${worldState.currentMap} (${worldState.player.x}, ${worldState.player.y})`);
+            warpToMap(targetMap, targetX, targetY);
+            console.log(`[gameMode] warped to ${targetMap} (${targetX}, ${targetY})`);
             break;
         }
 

js/world/maps.js

@@ -32,9 +32,9 @@ const labMap = {
     wallSet: buildWallSet(labWalls),
 
     exits: [
-        // No targetX/targetY — uses stored return point (the door the player entered from)
-        { x: 4, y: 11, targetMap: 'town' },
-        { x: 5, y: 11, targetMap: 'town' },
+        // Bidirectional: these doors return to the specific town door (12,12 = tile in front of lab entrance)
+        { x: 4, y: 11, targetMap: 'town', targetX: 12, targetY: 12 },
+        { x: 5, y: 11, targetMap: 'town', targetX: 12, targetY: 12 },
     ],
 
     npcs: [

js/world/worldState.js

@@ -40,10 +40,6 @@ export const worldState = {
     solvedPuzzles: [],  // array of puzzleIds that have been solved
     activePuzzle: null,  // { puzzleId, requiredOutputs, doorX, doorY } or null when no puzzle active
 
-    // Return points — remembers where the player entered each map from
-    // Stack of { fromMap, fromX, fromY } — push on enter, pop on exit
-    returnPoints: [],
-
     // Game flags
     flags: {
         // Examples: