diff --git a/game/README.md b/game/README.md
index 72d9af1..dc1cd0c 100644
--- a/game/README.md
+++ b/game/README.md
@@ -36,3 +36,9 @@ production reports the error and substitutes a bundled actor or plain stage plat
 Use `?region=rusty-creek&state=anomaly&inspect` on the dev URL to drag-pan the stage.
 `state=clean` selects the calm version. Export the assets before starting dev;
 the loader does not generate or copy art.
+
+Press **F2** to toggle the authored collision overlay (docs/04 colours). It uses
+the same world polylines and boxes that the controller consumes. Collision files
+are fetched next to the exported manifest, validated against the chunk and state,
+then shifted from chunk-local pixels by the manifest's grid coordinates. Original
+metadata is retained; reserved ledges and glide lifts do not become solid surfaces.
diff --git a/game/src/core/scaffold.ts b/game/src/core/scaffold.ts
index 3b64b7b..80f26ca 100644
--- a/game/src/core/scaffold.ts
+++ b/game/src/core/scaffold.ts
@@ -2,6 +2,8 @@ import Phaser from 'phaser';
 import { Assets, BOARDS } from '../stage/assets';
 import { drawStage } from '../stage/render';
 import type { StageManifest, RegionState } from '../stage/manifest';
+import { loadCollisions, type CollisionChunk } from '../stage/collision';
+import { collisionDebug } from '../stage/collision-debug';
 
 // Bootstrap-only scenes live in lane B until lane A provides story/UI scenes.
 export class Boot extends Phaser.Scene {
@@ -17,15 +19,17 @@ export class Preload extends Phaser.Scene {
     const state: RegionState = query.get('state') === 'clean' ? 'clean' : 'anomaly';
     const assets = new Assets(this);
     const manifest = await assets.stage(region, state);
+    const collisions = manifest.chunks[0].id === 'fallback' ? [] : await loadCollisions(manifest, state);
     for (const board of BOARDS) await assets.board(board);
-    this.scene.start('Stage', { manifest, state });
+    this.scene.start('Stage', { manifest, state, collisions });
   }
 }
 
 export class Stage extends Phaser.Scene {
   constructor() { super('Stage'); }
-  create(data: { manifest: StageManifest; state: RegionState }) {
+  create(data: { manifest: StageManifest; state: RegionState; collisions: CollisionChunk[] }) {
     drawStage(this, data.manifest, data.state);
+    collisionDebug(this, data.collisions);
     this.scene.launch('UI');
     // Development inspection only; camera follow is implemented separately in #32.
     if (import.meta.env.DEV && new URLSearchParams(location.search).has('inspect')) {
diff --git a/game/src/stage/collision-debug.ts b/game/src/stage/collision-debug.ts
new file mode 100644
index 0000000..0b857b2
--- /dev/null
+++ b/game/src/stage/collision-debug.ts
@@ -0,0 +1,30 @@
+import type Phaser from 'phaser';
+import { BOXES, LINES, POINTS, type CollisionChunk } from './collision';
+
+const COLOURS = { walk: 0x28dc3c, slide: 0x965a28, oneWay: 0xffdc00, climb: 0x286eff,
+  solid: 0xe61e1e, noGo: 0x000000, hazard: 0xff8c00, interact: 0xaa3cdc,
+  spawn: 0xffffff, ledge: 0x00e6e6, glideLift: 0xaad2ff };
+
+/** F2 toggles the authoring legend over the same world geometry used by physics. */
+export function collisionDebug(scene: Phaser.Scene, chunks: CollisionChunk[]) {
+  const graphics = scene.add.graphics().setDepth(10000).setVisible(false);
+  for (const { world } of chunks) {
+    for (const key of BOXES) for (const b of world[key]) {
+      graphics.fillStyle(COLOURS[key], 0.27).fillRect(b.x, b.y, b.w, b.h);
+      graphics.lineStyle(3, COLOURS[key]).strokeRect(b.x, b.y, b.w, b.h);
+    }
+    for (const key of LINES) for (const line of world[key]) {
+      graphics.lineStyle(5, COLOURS[key]).beginPath().moveTo(...line[0]);
+      for (const p of line.slice(1)) graphics.lineTo(...p);
+      graphics.strokePath();
+    }
+    for (const key of POINTS) for (const p of world[key]) {
+      graphics.fillStyle(COLOURS[key]).fillCircle(p.x, p.y, 6);
+      if (key === 'spawn' && p.kind === 'player') graphics.lineStyle(2, 0xffffff).strokeRect(p.x - 14, p.y - 76, 28, 76);
+    }
+  }
+  const toggle = () => graphics.setVisible(!graphics.visible);
+  scene.input.keyboard?.on('keydown-F2', toggle);
+  scene.events.once('shutdown', () => scene.input.keyboard?.off('keydown-F2', toggle));
+  return graphics;
+}
diff --git a/game/src/stage/collision.test.ts b/game/src/stage/collision.test.ts
new file mode 100644
index 0000000..6c637dc
--- /dev/null
+++ b/game/src/stage/collision.test.ts
@@ -0,0 +1,82 @@
+import { expect, it, vi } from 'vitest';
+import { loadCollisions, parseCollision, placeCollision, BOXES, LINES, type CollisionData } from './collision';
+import type { StageManifest } from './manifest';
+
+const fixtures = import.meta.glob<CollisionData>('../../../art/stages/{rusty-creek,hidden-garden}/*.collision.json',
+  { eager: true, import: 'default' });
+function fixture(chunk = 'rc-0-0', state: 'clean' | 'anomaly' = 'anomaly'): CollisionData {
+  const region = chunk.startsWith('hg-') ? 'hidden-garden' : 'rusty-creek';
+  const data = fixtures[`../../../art/stages/${region}/${chunk}.${state}.collision.json`];
+  if (!data) throw new Error(`Missing committed fixture ${chunk}.${state}`);
+  return structuredClone(data);
+}
+
+it('reads every committed jam collision file without discarding encounter metadata', () => {
+  for (const state of ['clean', 'anomaly'] as const) for (let x = 0; x < 3; x++) {
+    const id = `rc-${x}-0`, raw = fixture(id, state);
+    expect(parseCollision(raw, id, state)).toEqual(raw);
+  }
+  const garden = fixture('hg-0-0', 'clean');
+  expect(parseCollision(garden, 'hg-0-0', 'clean')).toEqual(garden);
+  const creek = parseCollision(fixture(), 'rc-0-0', 'anomaly');
+  expect(creek.interact.find(item => item.id === 'chair')?.item).toBe('chair');
+});
+
+it('places polylines, boxes, spawns and patrol bounds on a four-direction grid', () => {
+  const local = parseCollision(fixture(), 'rc-0-0', 'anomaly'), before = structuredClone(local);
+  const { world } = placeCollision(local, [2160, -720]);
+  expect(world.walk[0][0]).toEqual([2160, -259]);
+  expect(world.spawn.find(p => p.id === 'rover-1')).toMatchObject({ x: 2920, y: -212, patrol: [2800, 3040] });
+  expect(world.interact.find(p => p.id === 'chair')).toMatchObject({ x: 2476, y: -295, item: 'chair' });
+  expect(local).toEqual(before);
+});
+
+it('rejects missing categories, wrong identities and non-integer/outside points', () => {
+  for (const change of [(d: CollisionData) => { delete (d as Partial<CollisionData>).walk; }, (d: CollisionData) => { d.chunk = 'rc-2-0'; },
+    (d: CollisionData) => { d.state = 'clean'; }, (d: CollisionData) => { d.spawn[0].x = 0.5; },
+    (d: CollisionData) => { d.walk[0][0][1] = 721; }]) {
+    const raw = fixture(); change(raw);
+    expect(() => parseCollision(raw, 'rc-0-0', 'anomaly')).toThrow('Invalid collision');
+  }
+});
+
+it('rejects malformed lines, boxes, hazard damage and duplicate ids', () => {
+  for (const change of [(d: CollisionData) => { d.walk[0].reverse(); }, (d: CollisionData) => { d.solid[0].w = 0; },
+    (d: CollisionData) => { d.climb[0].kind = ''; }, (d: CollisionData) => { d.spawn[0].id = d.climb[0].id; },
+    (d: CollisionData) => { d.hazard.push({ x: 1, y: 1, w: 10, h: 10, damage: 0 }); }]) {
+    const raw = fixture(); change(raw);
+    expect(() => parseCollision(raw, 'rc-0-0', 'anomaly')).toThrow('Invalid collision');
+  }
+});
+
+it('retains reserved ledge and glide data without converting either to ground or walls', () => {
+  const raw = fixture(); raw.ledge.push({ x: 200, y: 100 });
+  raw.glideLift.push({ x: 300, y: 200, w: 50, h: 100 });
+  const { world } = placeCollision(parseCollision(raw, 'rc-0-0', 'anomaly'), [2160, 0]);
+  expect(world.ledge).toEqual([{ x: 2360, y: 100 }]);
+  expect(world.glideLift[0].x).toBe(2460);
+  for (const key of LINES) expect(world[key]).toHaveLength(raw[key].length);
+  expect(world.solid).toHaveLength(raw.solid.length);
+});
+
+function manifest(): StageManifest {
+  return { region: 'rusty-creek', chunkSize: [2160, 720], chunks: [0, 1].map(x => ({
+    id: `rc-${x}-0`, x, y: 0, states: { anomaly: { layers: [], collision: `rc-${x}-0.anomaly.collision.json` } },
+  })) };
+}
+
+it('fetches the collision files beside the manifest and builds world coordinates', async () => {
+  const request = vi.fn(async (url: string | URL | Request) => new Response(JSON.stringify(
+    fixture(String(url).includes('rc-1-0') ? 'rc-1-0' : 'rc-0-0'))));
+  const chunks = await loadCollisions(manifest(), 'anomaly', request);
+  expect(request).toHaveBeenCalledWith('/assets/stages/rusty-creek/rc-0-0.anomaly.collision.json');
+  expect(chunks[1].origin).toEqual([2160, 0]);
+  for (const key of BOXES) expect(chunks[1].world[key]).toHaveLength(chunks[1].local[key].length);
+});
+
+it('refuses a missing collision file instead of inferring physics from artwork', async () => {
+  const request = vi.fn(async () => new Response('', { status: 404 }));
+  await expect(loadCollisions(manifest(), 'anomaly', request)).rejects.toThrow('HTTP 404');
+  const input = manifest(); input.chunks[0].states.anomaly!.collision = null;
+  await expect(loadCollisions(input, 'anomaly', request)).rejects.toThrow('Missing collision:');
+});
diff --git a/game/src/stage/collision.ts b/game/src/stage/collision.ts
new file mode 100644
index 0000000..b7b72a8
--- /dev/null
+++ b/game/src/stage/collision.ts
@@ -0,0 +1,88 @@
+import { assetFile, type StageManifest, type RegionState } from './manifest';
+import { stageBase } from './assets';
+
+export type Point = [number, number];
+export interface Marker { x: number; y: number; id?: string; kind?: string; [key: string]: unknown }
+export interface Box extends Marker { w: number; h: number }
+export const LINES = ['walk', 'slide', 'oneWay'] as const;
+export const BOXES = ['climb', 'solid', 'noGo', 'hazard', 'interact', 'glideLift'] as const;
+export const POINTS = ['spawn', 'ledge'] as const;
+export type Geometry = Record<typeof LINES[number], Point[][]>
+  & Record<typeof BOXES[number], Box[]> & Record<typeof POINTS[number], Marker[]>;
+export type CollisionData = Geometry & { chunk: string; state: RegionState; size: [number, number] };
+export interface CollisionChunk { local: CollisionData; origin: Point; world: Geometry }
+
+function assert(condition: unknown, message: string): asserts condition {
+  if (!condition) throw new Error(`Invalid collision: ${message}`);
+}
+const object = (v: unknown): v is Record<string, unknown> => typeof v === 'object' && v !== null && !Array.isArray(v);
+const integer = (v: unknown): v is number => typeof v === 'number' && Number.isInteger(v);
+const kind = (v: unknown): v is string => typeof v === 'string' && /^[a-z][a-z0-9-]*$/.test(v);
+
+/** Read authored shapes only. Reserved ledges and glide lifts never become solids. */
+export function parseCollision(value: unknown, chunk: string, state: RegionState): CollisionData {
+  assert(object(value) && value.chunk === chunk && value.state === state, `${chunk}.${state} identity`);
+  assert(Array.isArray(value.size) && value.size.length === 2 && value.size[0] === 2160 && value.size[1] === 720, 'size');
+  const inside = (x: unknown, y: unknown) => {
+    assert(integer(x) && integer(y) && x >= 0 && x <= 2160 && y >= 0 && y <= 720, 'integer point outside chunk');
+  };
+  const ids = new Set<string>();
+  for (const key of [...LINES, ...BOXES, ...POINTS]) {
+    const entries = value[key];
+    assert(Array.isArray(entries), `${key} must be an array`);
+    if ((LINES as readonly string[]).includes(key)) {
+      for (const line of entries) {
+        assert(Array.isArray(line) && line.length >= 2, `${key} polyline`);
+        for (const p of line) { assert(Array.isArray(p) && p.length === 2, `${key} point`); inside(p[0], p[1]); }
+        assert(line.every((p, i) => i === 0 || p[0] > line[i - 1][0]), `${key} must run left to right`);
+      }
+      continue;
+    }
+    for (const item of entries) {
+      assert(object(item), `${key} object`); inside(item.x, item.y);
+      if ((BOXES as readonly string[]).includes(key)) {
+        assert(integer(item.w) && integer(item.h) && item.w > 0 && item.h > 0, `${key} box dimensions`);
+        inside(Number(item.x) + item.w, Number(item.y) + item.h);
+      }
+      if (key === 'climb' || key === 'interact' || key === 'spawn') assert(kind(item.kind), `${key} kind`);
+      if (key === 'interact' || key === 'spawn') assert(typeof item.id === 'string' && item.id.length > 0, `${key} id`);
+      if (item.id !== undefined) {
+        assert(typeof item.id === 'string' && item.id.length > 0 && !ids.has(item.id), 'duplicate/invalid id');
+        ids.add(item.id);
+      }
+      if (key === 'hazard') assert(integer(item.damage) && item.damage > 0, 'hazard damage');
+    }
+  }
+  return value as unknown as CollisionData;
+}
+
+/** Grid offsets apply to geometry and local horizontal patrol bounds, not metadata. */
+export function placeCollision(local: CollisionData, origin: Point): CollisionChunk {
+  const [dx, dy] = origin;
+  const marker = <T extends Marker>(item: T): T => ({ ...item, x: item.x + dx, y: item.y + dy });
+  const world = Object.fromEntries([
+    ...LINES.map(key => [key, local[key].map(line => line.map(([x, y]): Point => [x + dx, y + dy]))]),
+    ...BOXES.map(key => [key, local[key].map(marker)]),
+    ...POINTS.map(key => [key, local[key].map(item => {
+      const placed = marker(item);
+      if (key === 'spawn' && Array.isArray(item.patrol) && item.patrol.every(v => typeof v === 'number')) {
+        placed.patrol = item.patrol.map(x => x + dx);
+      }
+      return placed;
+    })]),
+  ]) as Geometry;
+  return { local, origin, world };
+}
+
+export async function loadCollisions(manifest: StageManifest, state: RegionState,
+  request: typeof fetch = (...args) => fetch(...args)): Promise<CollisionChunk[]> {
+  return Promise.all(manifest.chunks.map(async chunk => {
+    const file = chunk.states[state]?.collision;
+    if (!assetFile(file)) throw new Error(`Missing collision: ${manifest.region}/${chunk.id}.${state}`);
+    const url = stageBase(manifest.region) + file;
+    const response = await request(url);
+    if (!response.ok) throw new Error(`Missing collision ${url}: HTTP ${response.status}`);
+    return placeCollision(parseCollision(await response.json(), chunk.id, state),
+      [chunk.x * manifest.chunkSize[0], chunk.y * manifest.chunkSize[1]]);
+  }));
+}