docs: add Milestone 8 implementation plan

6-task TDD plan covering assets.scm, render-scene!, engine.scm,
game-run!, Makefile updates, and macroknight port.

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

1 files changed, 826 insertions, 0 deletions

diff --git a/docs/superpowers/plans/2026-04-05-milestone-8-game-object-lifecycle.md b/docs/superpowers/plans/2026-04-05-milestone-8-game-object-lifecycle.md
new file mode 100644
index 0000000..0d12308
--- /dev/null
+++ b/docs/superpowers/plans/2026-04-05-milestone-8-game-object-lifecycle.md
@@ -0,0 +1,826 @@
+# Milestone 8 — Game Object and Lifecycle API
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Introduce `make-game` + `game-run!` as the public entry point for downstroke, backed by a minimal asset registry, and port macroknight to use them.
+
+**Architecture:** Two new modules (`assets.scm` — key/value registry; `engine.scm` — game struct, lifecycle, frame loop), plus `render-scene!` added to `renderer.scm`. `game-run!` owns SDL2 init, window/renderer creation, and the frame loop; lifecycle hooks (`preload:`, `create:`, `update:`, `render:`) are user-supplied lambdas.
+
+**Tech Stack:** Chicken Scheme, SDL2 (sdl2 egg), sdl2-ttf, sdl2-image, SRFI-64 (tests), defstruct egg
+
+**Spec:** `docs/superpowers/specs/2026-04-05-milestone-8-game-object-lifecycle-design.md`
+
+---
+
+## File Map
+
+| Action | File | Purpose |
+|---|---|---|
+| Create | `assets.scm` | Key→value asset registry |
+| Create | `tests/assets-test.scm` | SRFI-64 unit tests for assets.scm |
+| Modify | `renderer.scm` | Add `render-scene!` |
+| Modify | `tests/renderer-test.scm` | Add tests for `render-scene!` |
+| Create | `engine.scm` | `make-game`, `game-run!`, accessors |
+| Create | `tests/engine-test.scm` | Unit tests for make-game, accessors (SDL2 mocked) |
+| Modify | `Makefile` | Add assets + engine to build, add test targets |
+| Modify | `/home/gene/src/macroknight/game.scm` | Port to `make-game` + `game-run!` |
+
+---
+
+## Task 1: `assets.scm` — minimal key/value registry
+
+**Files:**
+- Create: `assets.scm`
+- Create: `tests/assets-test.scm`
+
+### What this module does
+
+A thin wrapper around a hash table. No asset-type logic — that's Milestone 6. Three public functions:
+
+```scheme
+(make-asset-registry)          ;; → hash-table
+(asset-set! registry key val)  ;; → unspecified (mutates)
+(asset-ref registry key)       ;; → value or #f if missing
+```
+
+- [ ] **Step 1: Write the failing tests**
+
+Create `tests/assets-test.scm`:
+
+```scheme
+(import scheme (chicken base) srfi-64)
+
+(include "assets.scm")
+(import downstroke/assets)
+
+(test-begin "assets")
+
+(test-group "make-asset-registry"
+  (test-assert "returns a value"
+    (make-asset-registry)))
+
+(test-group "asset-set! and asset-ref"
+  (let ((reg (make-asset-registry)))
+    (test-equal "missing key returns #f"
+      #f
+      (asset-ref reg 'missing))
+
+    (asset-set! reg 'my-tilemap "data")
+    (test-equal "stored value is retrievable"
+      "data"
+      (asset-ref reg 'my-tilemap))
+
+    (asset-set! reg 'my-tilemap "updated")
+    (test-equal "overwrite replaces value"
+      "updated"
+      (asset-ref reg 'my-tilemap))
+
+    (asset-set! reg 'other 42)
+    (test-equal "multiple keys coexist"
+      "updated"
+      (asset-ref reg 'my-tilemap))
+    (test-equal "second key retrievable"
+      42
+      (asset-ref reg 'other))))
+
+(test-end "assets")
+```
+
+- [ ] **Step 2: Run test to confirm it fails**
+
+```bash
+cd /home/gene/src/downstroke
+csi -s tests/assets-test.scm
+```
+
+Expected: error — `assets.scm` not found / `downstroke/assets` not defined.
+
+- [ ] **Step 3: Implement `assets.scm`**
+
+Create `assets.scm`:
+
+```scheme
+(module downstroke/assets *
+
+(import scheme
+        (chicken base)
+        (srfi 69))
+
+(define (make-asset-registry)
+  (make-hash-table))
+
+(define (asset-set! registry key value)
+  (hash-table-set! registry key value))
+
+(define (asset-ref registry key)
+  (hash-table-ref/default registry key #f))
+
+) ;; end module
+```
+
+- [ ] **Step 4: Run test to confirm it passes**
+
+```bash
+cd /home/gene/src/downstroke
+csi -s tests/assets-test.scm
+```
+
+Expected: all tests pass, no failures reported.
+
+- [ ] **Step 5: Commit**
+
+```bash
+cd /home/gene/src/downstroke
+git add assets.scm tests/assets-test.scm
+git commit -m "feat: add assets.scm — minimal key/value asset registry"
+```
+
+---
+
+## Task 2: Add `render-scene!` to `renderer.scm`
+
+**Files:**
+- Modify: `renderer.scm` (add one function after `draw-entities`)
+- Modify: `tests/renderer-test.scm` (add one test group)
+
+### What this adds
+
+`render-scene!` draws a complete scene (all tilemap layers + all entities) given a renderer and a scene struct. It delegates to the already-tested `draw-tilemap` and `draw-entities`.
+
+Existing signatures in `renderer.scm`:
+- `(draw-tilemap renderer camera tileset-texture tilemap)` — 4 args
+- `(draw-entities renderer camera tileset tileset-texture entities)` — 5 args
+
+The `tileset` is extracted from `tilemap` via the `tilemap-tileset` accessor (from `tilemap.scm`).
+
+- [ ] **Step 1: Write the failing test**
+
+Add to `tests/renderer-test.scm`, before `(test-end "renderer")`:
+
+```scheme
+(test-group "render-scene!"
+  ;; render-scene! calls draw-tilemap and draw-entities — both are mocked to return #f.
+  ;; We verify it doesn't crash on a valid scene and returns unspecified.
+  (let* ((cam      (make-camera x: 0 y: 0))
+         (tileset  (make-tileset tilewidth: 16 tileheight: 16
+                                 spacing: 0 tilecount: 100 columns: 10
+                                 image-source: "" image: #f))
+         (layer    (make-layer name: "ground" width: 2 height: 2
+                               map: '((1 2) (3 4))))
+         (tilemap  (make-tilemap width: 2 height: 2
+                                 tilewidth: 16 tileheight: 16
+                                 tileset-source: ""
+                                 tileset: tileset
+                                 layers: (list layer)
+                                 objects: '()))
+         (scene    (make-scene entities: '()
+                               tilemap: tilemap
+                               camera: cam
+                               tileset-texture: #f)))
+    (test-assert "does not crash on valid scene"
+      (begin (render-scene! #f scene) #t))))
+```
+
+- [ ] **Step 2: Run test to confirm it fails**
+
+```bash
+cd /home/gene/src/downstroke
+csi -s tests/renderer-test.scm
+```
+
+Expected: error — `render-scene!` not defined.
+
+- [ ] **Step 3: Add `render-scene!` to `renderer.scm`**
+
+Add after the `draw-entities` definition (before the closing `)`):
+
+```scheme
+  ;; --- Scene drawing ---
+
+  (define (render-scene! renderer scene)
+    (let ((camera          (scene-camera scene))
+          (tilemap         (scene-tilemap scene))
+          (tileset-texture (scene-tileset-texture scene))
+          (tileset         (tilemap-tileset (scene-tilemap scene)))
+          (entities        (scene-entities scene)))
+      (draw-tilemap renderer camera tileset-texture tilemap)
+      (draw-entities renderer camera tileset tileset-texture entities)))
+```
+
+- [ ] **Step 4: Run tests to confirm they pass**
+
+```bash
+cd /home/gene/src/downstroke
+csi -s tests/renderer-test.scm
+```
+
+Expected: all tests pass.
+
+- [ ] **Step 5: Commit**
+
+```bash
+cd /home/gene/src/downstroke
+git add renderer.scm tests/renderer-test.scm
+git commit -m "feat: add render-scene! to renderer — draw full scene in one call"
+```
+
+---
+
+## Task 3: `engine.scm` — game struct, constructor, accessors
+
+**Files:**
+- Create: `engine.scm`
+- Create: `tests/engine-test.scm`
+
+This task covers only the data structure and constructor — no `game-run!` yet. TDD applies to the parts we can unit-test (struct creation, accessors).
+
+`game-run!` requires a live SDL2 window and cannot be unit-tested; it is tested in Task 6 via macroknight integration.
+
+### Mock strategy for tests
+
+`engine.scm` imports `renderer.scm`, `input.scm`, `world.scm`, `assets.scm`, and the SDL2 sub-libraries. The test file follows the same mock-module pattern as `tests/renderer-test.scm`: define mock modules that satisfy the imports, then `(include "engine.scm")`.
+
+- [ ] **Step 1: Write the failing tests**
+
+Create `tests/engine-test.scm`:
+
+```scheme
+(import scheme (chicken base) (chicken keyword) srfi-64 defstruct)
+
+;; --- Mocks ---
+
+(module sdl2 *
+  (import scheme (chicken base))
+  (define (set-main-ready!) #f)
+  (define (init! . args) #f)
+  (define (quit! . args) #f)
+  (define (get-ticks) 0)
+  (define (delay! ms) #f)
+  (define (pump-events!) #f)
+  (define (has-events?) #f)
+  (define (make-event) #f)
+  (define (poll-event! e) #f)
+  (define (num-joysticks) 0)
+  (define (is-game-controller? i) #f)
+  (define (game-controller-open! i) #f)
+  (define (create-window! . args) 'mock-window)
+  (define (create-renderer! . args) 'mock-renderer)
+  (define (destroy-window! . args) #f)
+  (define (render-clear! . args) #f)
+  (define (render-present! . args) #f))
+(import (prefix sdl2 "sdl2:"))
+
+(module sdl2-ttf *
+  (import scheme (chicken base))
+  (define (init!) #f))
+(import (prefix sdl2-ttf "ttf:"))
+
+(module sdl2-image *
+  (import scheme (chicken base))
+  (define (init! . args) #f))
+(import (prefix sdl2-image "img:"))
+
+;; --- Real deps (include order follows dependency order) ---
+(import simple-logger)   ;; required by input.scm
+(include "entity.scm")   (import downstroke/entity)
+(include "tilemap.scm")  (import downstroke/tilemap)
+(include "world.scm")    (import downstroke/world)
+(include "input.scm")    (import downstroke/input)
+(include "assets.scm")   (import downstroke/assets)
+
+;; Mock renderer (render-scene! can't run without real SDL2)
+(module downstroke/renderer *
+  (import scheme (chicken base))
+  (define (render-scene! . args) #f))
+(import downstroke/renderer)
+
+(include "engine.scm")
+(import downstroke/engine)
+
+;; --- Tests ---
+
+(test-begin "engine")
+
+(test-group "make-game defaults"
+  (let ((g (make-game)))
+    (test-equal "default title"
+      "Downstroke Game"
+      (game-title g))
+    (test-equal "default width"
+      640
+      (game-width g))
+    (test-equal "default height"
+      480
+      (game-height g))
+    (test-equal "default frame-delay"
+      16
+      (game-frame-delay g))
+    (test-equal "scene starts as #f"
+      #f
+      (game-scene g))
+    (test-equal "window starts as #f"
+      #f
+      (game-window g))
+    (test-equal "renderer starts as #f"
+      #f
+      (game-renderer g))
+    (test-assert "assets registry is created"
+      (game-assets g))
+    (test-assert "input state is created"
+      (game-input g))))
+
+(test-group "make-game with keyword args"
+  (let ((g (make-game title: "My Game" width: 320 height: 240 frame-delay: 33)))
+    (test-equal "custom title" "My Game" (game-title g))
+    (test-equal "custom width" 320 (game-width g))
+    (test-equal "custom height" 240 (game-height g))
+    (test-equal "custom frame-delay" 33 (game-frame-delay g))))
+
+(test-group "game-asset and game-asset-set!"
+  (let ((g (make-game)))
+    (test-equal "missing key returns #f"
+      #f
+      (game-asset g 'no-such-asset))
+    (game-asset-set! g 'my-font 'font-object)
+    (test-equal "stored asset is retrievable"
+      'font-object
+      (game-asset g 'my-font))
+    (game-asset-set! g 'my-font 'updated-font)
+    (test-equal "overwrite replaces asset"
+      'updated-font
+      (game-asset g 'my-font))))
+
+(test-group "make-game hooks default to #f"
+  (let ((g (make-game)))
+    (test-equal "preload-hook is #f" #f (game-preload-hook g))
+    (test-equal "create-hook is #f"  #f (game-create-hook g))
+    (test-equal "update-hook is #f"  #f (game-update-hook g))
+    (test-equal "render-hook is #f"  #f (game-render-hook g))))
+
+(test-group "make-game accepts hook lambdas"
+  (let* ((called #f)
+         (g (make-game update: (lambda (game dt) (set! called #t)))))
+    (test-assert "update hook is stored"
+      (procedure? (game-update-hook g)))))
+
+(test-end "engine")
+```
+
+- [ ] **Step 2: Run test to confirm it fails**
+
+```bash
+cd /home/gene/src/downstroke
+csi -s tests/engine-test.scm
+```
+
+Expected: error — `engine.scm` not found.
+
+- [ ] **Step 3: Implement `engine.scm` struct + constructor + accessors (no `game-run!`)**
+
+Create `engine.scm`. `game-run!` is a stub for now — it will be filled in Task 4.
+
+```scheme
+(module downstroke/engine *
+
+(import scheme
+        (chicken base)
+        (chicken keyword)
+        (prefix sdl2 "sdl2:")
+        (prefix sdl2-ttf "ttf:")
+        (prefix sdl2-image "img:")
+        defstruct
+        downstroke/world
+        downstroke/input
+        downstroke/assets
+        downstroke/renderer)
+
+;; ── Game struct ────────────────────────────────────────────────────────────
+;; constructor: make-game* (raw) so we can define make-game as keyword wrapper
+
+(defstruct (game constructor: make-game*)
+  title width height
+  window renderer
+  input          ;; input-state record
+  input-config   ;; input-config record
+  assets         ;; asset registry (hash-table from assets.scm)
+  frame-delay
+  preload-hook   ;; (lambda (game) ...)
+  create-hook    ;; (lambda (game) ...)
+  update-hook    ;; (lambda (game dt) ...)
+  render-hook    ;; (lambda (game) ...) — post-render overlay
+  scene)         ;; current scene struct; #f until create: runs
+
+;; ── Public constructor ─────────────────────────────────────────────────────
+
+(define (make-game #!key
+    (title "Downstroke Game")
+    (width 640) (height 480)
+    (frame-delay 16)
+    (input-config *default-input-config*)
+    (preload #f) (create #f) (update #f) (render #f))
+  (make-game*
+    title:        title
+    width:        width
+    height:       height
+    window:       #f
+    renderer:     #f
+    scene:        #f
+    input:        (create-input-state input-config)
+    input-config: input-config
+    assets:       (make-asset-registry)
+    frame-delay:  frame-delay
+    preload-hook: preload
+    create-hook:  create
+    update-hook:  update
+    render-hook:  render))
+
+;; ── Convenience accessors ──────────────────────────────────────────────────
+
+;; game-camera: derived from the current scene (only valid after create: runs)
+(define (game-camera game)
+  (scene-camera (game-scene game)))
+
+;; game-asset: retrieve an asset by key
+(define (game-asset game key)
+  (asset-ref (game-assets game) key))
+
+;; game-asset-set!: store an asset by key
+(define (game-asset-set! game key value)
+  (asset-set! (game-assets game) key value))
+
+;; ── game-run! ──────────────────────────────────────────────────────────────
+;; Stub — implemented in Task 4
+
+(define (game-run! game)
+  (error "game-run! not yet implemented"))
+
+) ;; end module
+```
+
+- [ ] **Step 4: Run tests to confirm they pass**
+
+```bash
+cd /home/gene/src/downstroke
+csi -s tests/engine-test.scm
+```
+
+Expected: all tests pass.
+
+- [ ] **Step 5: Commit**
+
+```bash
+cd /home/gene/src/downstroke
+git add engine.scm tests/engine-test.scm
+git commit -m "feat: add engine.scm — game struct, make-game constructor, accessors"
+```
+
+---
+
+## Task 4: Implement `game-run!`
+
+**Files:**
+- Modify: `engine.scm` (replace stub with real implementation)
+
+`game-run!` is tested via macroknight integration in Task 6, not via unit tests (it requires a real SDL2 display).
+
+- [ ] **Step 1: Replace the `game-run!` stub in `engine.scm`**
+
+Replace the stub `(define (game-run! game) (error ...))` with:
+
+```scheme
+(define (game-run! game)
+  ;; 1. SDL2 init (audio excluded — mixer.scm not yet extracted;
+  ;;    user calls init-audio! in their preload: hook)
+  (sdl2:set-main-ready!)
+  (sdl2:init! '(video joystick game-controller))
+  (ttf:init!)
+  (img:init! '(png))
+
+  ;; Open any already-connected game controllers
+  (let init-controllers ((i 0))
+    (when (< i (sdl2:num-joysticks))
+      (when (sdl2:is-game-controller? i)
+        (sdl2:game-controller-open! i))
+      (init-controllers (+ i 1))))
+
+  ;; 2. Create window + renderer
+  (game-window-set! game
+    (sdl2:create-window! (game-title game) 'centered 'centered
+                         (game-width game) (game-height game) '()))
+  (game-renderer-set! game
+    (sdl2:create-renderer! (game-window game) -1 '(accelerated vsync)))
+
+  ;; 3. preload: hook — user loads assets here
+  (when (game-preload-hook game)
+    ((game-preload-hook game) game))
+
+  ;; 4. create: hook — user builds initial scene here
+  (when (game-create-hook game)
+    ((game-create-hook game) game))
+
+  ;; 5. Frame loop
+  (let loop ((last-ticks (sdl2:get-ticks)))
+    (let* ((now    (sdl2:get-ticks))
+           (dt     (- now last-ticks)))
+      ;; Collect all pending SDL2 events
+      (sdl2:pump-events!)
+      (let* ((events (let collect ((lst '()))
+                       (if (not (sdl2:has-events?))
+                           (reverse lst)
+                           (let ((e (sdl2:make-event)))
+                             (sdl2:poll-event! e)
+                             (collect (cons e lst))))))
+             (input  (input-state-update (game-input game) events
+                                         (game-input-config game))))
+        (game-input-set! game input)
+        (unless (input-held? input 'quit)
+          ;; update: hook — user game logic
+          (when (game-update-hook game)
+            ((game-update-hook game) game dt))
+          ;; render: engine draws world, then user overlay
+          (sdl2:render-clear! (game-renderer game))
+          (when (game-scene game)
+            (render-scene! (game-renderer game) (game-scene game)))
+          (when (game-render-hook game)
+            ((game-render-hook game) game))
+          (sdl2:render-present! (game-renderer game))
+          (sdl2:delay! (game-frame-delay game))
+          (loop now)))))
+
+  ;; 6. Cleanup
+  (sdl2:destroy-window! (game-window game))
+  (sdl2:quit!))
+```
+
+Note: `sdl2:pump-events!` processes the OS event queue; `sdl2:has-events?`/`sdl2:make-event`/`sdl2:poll-event!` drain it into a list. This matches the pattern used in macroknight's existing game loop (lines 661–667).
+
+**Spec discrepancy:** The spec document shows `(sdl2:collect-events!)` in its pseudocode — that function does not exist in the sdl2 egg. The plan's pump+collect loop above is the correct implementation. Ignore the spec's `sdl2:collect-events!` reference.
+
+- [ ] **Step 2: Verify engine-test.scm still passes**
+
+```bash
+cd /home/gene/src/downstroke
+csi -s tests/engine-test.scm
+```
+
+Expected: all tests pass (game-run! itself is not called in unit tests).
+
+- [ ] **Step 3: Commit**
+
+```bash
+cd /home/gene/src/downstroke
+git add engine.scm tests/engine-test.scm
+git commit -m "feat: implement game-run! — SDL2 init, lifecycle hooks, frame loop"
+```
+
+---
+
+## Task 5: Update the Makefile
+
+**Files:**
+- Modify: `Makefile`
+
+- [ ] **Step 1: Add `assets` and `engine` to `MODULE_NAMES`**
+
+In `Makefile`, change:
+```makefile
+MODULE_NAMES := entity tilemap world input physics renderer
+```
+to:
+```makefile
+MODULE_NAMES := entity tilemap world input physics renderer assets engine
+```
+
+- [ ] **Step 2: Add dependency declarations**
+
+Add after `bin/renderer.o: bin/entity.o bin/tilemap.o bin/world.o`:
+
+```makefile
+bin/assets.o:
+bin/engine.o: bin/renderer.o bin/world.o bin/input.o bin/assets.o
+```
+
+`assets.scm` has no inter-module dependencies. `engine.scm` depends on renderer, world, input, and assets.
+
+- [ ] **Step 3: Add test targets**
+
+In the `test:` rule, add:
+```makefile
+	@csi -s tests/assets-test.scm
+	@csi -s tests/engine-test.scm
+```
+
+- [ ] **Step 4: Verify the build**
+
+```bash
+cd /home/gene/src/downstroke
+make clean && make
+```
+
+Expected: all `.o` files created in `bin/`, including `bin/assets.o` and `bin/engine.o`. No errors.
+
+- [ ] **Step 5: Run all tests**
+
+```bash
+cd /home/gene/src/downstroke
+make test
+```
+
+Expected: all test suites pass.
+
+- [ ] **Step 6: Commit**
+
+```bash
+cd /home/gene/src/downstroke
+git add Makefile
+git commit -m "build: add assets and engine modules to Makefile"
+```
+
+---
+
+## Task 6: Port macroknight to `make-game` + `game-run!`
+
+**Files:**
+- Modify: `/home/gene/src/macroknight/game.scm`
+
+This is the integration test for the whole milestone. macroknight's current `game.scm` is ~678 lines with SDL2 init, the frame loop, and all game state mixed together. After this task it should be ≤50 lines: only `make-game`, the three lifecycle hooks, and `game-run!`.
+
+### What moves vs. what stays
+
+**Moves to engine (delete from game.scm):**
+- Lines 87–137: SDL2 init block — from `(sdl2:set-main-ready!)` through `(define *title-font* ...)` inclusive. This covers: `sdl2:set-main-ready!`, `sdl2:init!`, `init-game-controllers!` call, `ttf:init!`, `img:init!`, audio init calls, `on-exit` handlers, exception handler wrapper, `sdl2:set-hint!`, `sdl2:create-window!`, `sdl2:create-renderer!`, `ttf:open-font` calls.
+- Lines 659–673: The main `let/cc` game loop
+
+**Stays in macroknight (wrapped in lifecycle hooks):**
+- `init-audio!` + `load-sounds!` + `load-music!` → `preload:` hook
+- `ttf:open-font` calls (fonts) → `preload:` hook
+- `make-initial-game-state` → `create:` hook
+- `update-game-state` dispatch → `update:` hook
+- `render-frame` mode dispatch (minus clear/present) → `render:` hook
+
+**macroknight-specific state** (`game-state` struct: mode, menu-cursor, scene, input, etc.) stays as the module-level `*gs*` variable — set in `create:`, mutated in `update:`.
+
+**`render-frame` split:** The existing `render-frame` calls `sdl2:render-clear!` and `sdl2:render-present!` — those are now owned by the engine. Modify `render-frame` to remove those two calls, keeping only the draw-color set and the mode dispatch. The modified `render-frame` becomes the body of the `render:` hook. Since the background color is black (`0 0 0`) and the engine's clear already clears to black, there is no visual difference.
+
+### Implementation steps
+
+- [ ] **Step 1: Add `downstroke/engine` to macroknight's imports**
+
+In `/home/gene/src/macroknight/game.scm`, add to the import list:
+```scheme
+downstroke/engine
+downstroke/assets
+```
+
+- [ ] **Step 2: Restructure as `make-game` call**
+
+Replace the top-level SDL2 init block and the game loop at the bottom of `game.scm` with a `make-game` call. The three lifecycle hooks capture the existing functions from the rest of the file.
+
+**First, modify `render-frame`** to remove the SDL2 clear/present calls (the engine now owns those). Change lines 378–385 of `game.scm` from:
+
+```scheme
+(define (render-frame gs)
+  (set! (sdl2:render-draw-color *renderer*) +background-color+)
+  (sdl2:render-clear! *renderer*)
+  (case (game-state-mode gs)
+    ((main-menu)    (draw-main-menu    gs))
+    ((stage-select) (draw-stage-select gs))
+    ((playing)      (draw-playing      gs)))
+  (sdl2:render-present! *renderer*))
+```
+
+to:
+
+```scheme
+(define (render-frame gs)
+  (set! (sdl2:render-draw-color *renderer*) +background-color+)
+  (case (game-state-mode gs)
+    ((main-menu)    (draw-main-menu    gs))
+    ((stage-select) (draw-stage-select gs))
+    ((playing)      (draw-playing      gs))))
+```
+
+**Then add module-level state and the engine entry point** at the bottom of `game.scm` (replacing the old `let/cc` loop):
+
+```scheme
+;; ── Module-level game state ────────────────────────────────────────────────
+
+(define *gs* #f)  ;; macroknight game state, set in create:
+
+;; ── Engine entry point ─────────────────────────────────────────────────────
+
+(define *the-game*
+  (make-game
+    title:       "MacroKnight"
+    width:       +screen-width+
+    height:      +screen-height+
+    frame-delay: 10
+
+    preload: (lambda (game)
+               ;; Audio (mixer not yet extracted — call directly)
+               (init-audio!)
+               (load-sounds! '((jump . "assets/jump.wav")))
+               (load-music!  "assets/theme.ogg")
+               (play-music!  0.6)
+               ;; Fonts
+               (set! *font*       (ttf:open-font "assets/DejaVuSans.ttf" 12))
+               (set! *title-font* (ttf:open-font "assets/DejaVuSans.ttf" 32))
+               ;; Make the SDL2 renderer available to macroknight functions
+               (set! *renderer* (game-renderer game)))
+
+    create: (lambda (game)
+              (set! *gs* (make-initial-game-state)))
+
+    update: (lambda (game dt)
+              ;; update-game-state uses a continuation for the "quit" menu item;
+              ;; pass a no-op since the engine handles Escape→quit automatically.
+              (update-game-state *gs* (lambda () #f))
+              (maybe-advance-level *gs*))
+
+    render: (lambda (game)
+              ;; engine has already called render-clear! and render-scene!
+              ;; (game-scene is #f so render-scene! is a no-op for now);
+              ;; render-frame draws the mode-specific content.
+              (render-frame *gs*))))
+
+(game-run! *the-game*)
+```
+
+**Notes:**
+- `*renderer*`, `*font*`, `*title-font*` remain module-level variables (set in `preload:`). Keep their `(define ...)` declarations at the top of `game.scm` as `(define *font* #f)` etc. (uninitialized — they'll be set in `preload:`).
+- The engine's input handles Escape → quit via `input-held? input 'quit`; the old `let/cc exit-main-loop!` mechanism and `exit-main-loop!` call in `update-game-state` are no longer needed. **However, do not change `update-game-state` in this milestone** — the `(lambda () #f)` passed as `exit!` means the "Quit" menu item is a no-op for now. Fix it in a later milestone.
+- `(game-scene game)` is never set from macroknight, so the engine's `render-scene!` is always a no-op. All rendering happens in the `render:` hook via `render-frame`. This is intentional for this port milestone.
+
+- [ ] **Step 3: Remove the old SDL2 init block from `game.scm`**
+
+Delete lines 87–137 — everything from `(sdl2:set-main-ready!)` through `(define *title-font* (ttf:open-font ...))` inclusive.
+
+This also removes the `on-exit` cleanup handlers (lines 107–108) and the custom exception handler (lines 113–117). **This is intentional for this milestone.** The engine's `game-run!` calls `sdl2:destroy-window!` and `sdl2:quit!` at cleanup, but does not install an exception handler. If macroknight crashes mid-run, SDL2 will not be shut down cleanly. This will be addressed in a later milestone (either by adding error handling to `game-run!` or by macroknight wrapping `game-run!` in a guard).
+
+After deletion, add these uninitialized stubs near the top of `game.scm` (after the imports) so the rest of the file can still reference the variables. Note: `*window*` only appears inside the deleted range, so its stub is precautionary only.
+
+```scheme
+(define *window*     #f)  ;; owned by engine; not used after this port
+(define *renderer*   #f)  ;; set in preload:
+(define *font*       #f)  ;; set in preload:
+(define *title-font* #f)  ;; set in preload:
+(define *text-color* (sdl2:make-color 255 255 255))
+```
+
+- [ ] **Step 4: Remove the old main loop from `game.scm`**
+
+Delete lines 659–678 (the `let/cc` game loop through the end of the file including the `"Bye!\n"` print). The engine's `game-run!` replaces it. The new `(define *the-game* ...)` and `(game-run! *the-game*)` from Step 2 are the new end of the file.
+
+- [ ] **Step 5: Build macroknight to verify it compiles**
+
+```bash
+cd /home/gene/src/macroknight
+make clean && make
+```
+
+Expected: successful compilation. Fix any symbol-not-found or import errors before continuing.
+
+- [ ] **Step 6: Run macroknight to verify it plays**
+
+```bash
+cd /home/gene/src/macroknight
+./bin/game
+```
+
+Expected: game launches, title screen appears, gameplay works correctly (title → stage select → play a level). Press Escape to quit.
+
+**Known regression (intentional):** Selecting "Quit" from the main menu is a no-op in this milestone. The old `exit-main-loop!` continuation no longer exists; the `update:` hook passes `(lambda () #f)` in its place. This will be fixed in a later milestone.
+
+- [ ] **Step 7: Verify game.scm is ≤50 lines**
+
+```bash
+wc -l /home/gene/src/macroknight/game.scm
+```
+
+If still over 50 lines, extract helper functions that belong in other modules. Game-specific logic (menu rendering, level loading) can stay; SDL2 boilerplate must be gone.
+
+- [ ] **Step 8: Commit**
+
+```bash
+cd /home/gene/src/macroknight
+git add game.scm
+git commit -m "feat: port macroknight to use make-game + game-run! (Milestone 8)"
+```
+
+Then commit the downstroke side:
+
+```bash
+cd /home/gene/src/downstroke
+git add -A
+git commit -m "feat: Milestone 8 complete — make-game + game-run! engine entry point"
+```
+
+---
+
+## Acceptance Criteria
+
+- [ ] `make test` in downstroke passes all suites including assets and engine
+- [ ] `make` in downstroke builds all modules including `bin/assets.o` and `bin/engine.o`
+- [ ] `make && ./bin/game` in macroknight launches and plays correctly
+- [ ] macroknight `game.scm` is ≤50 lines with no SDL2 init or frame-loop boilerplate
+- [ ] `make-game` + `game-run!` are the sole entry point — no top-level SDL2 calls outside them