Compositor

Build a tiny browser game called "Compositor".

Game spec
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A film compositor's bench rebuilding a shot from its layers. A stack of celluloid strips sits on a light table — foreground matte, subject cutout, background plate, and a rostrum camera move — and the finished frame has to match the reference frame shown in the corner. Drag a layer into position with the mouse or a touch drag, or nudge the selected layer with the arrow keys and rotate it with the brackets; toggle a layer's matte with Space and change its opacity step with PageUp/PageDown. The trap is that each layer carries its own offset and scale error from the original camera move, so the shot only registers when all of them are right at once, and a layer that looks locally aligned still throws the composite somewhere else. A difference view (key D) shows misregistration as red fringing so errors are readable rather than guessed, and a registration percentage climbs as you close in. Locking all layers inside tolerance prints the frame for points scaled by how few adjustments you used and how close the final registration is, then the next shot has another layer, a pan to track, and a tighter tolerance. Three shots on easy, one on hard, with a frame counter ticking down. Editing-room look: warm light table with a bright rectangle, sprocket-holed film strips with visible grain, grease-pencil alignment marks, a splicing block, a rewound reel, and a projector whir and a splice-tape rip in WebAudio.

Hard constraints — the game will be embedded in a sandboxed iframe on a static gallery site, and a headless browser will screenshot it:

1. Output exactly ONE self-contained HTML file. All CSS and JS inline. Zero external requests: no CDNs, no external fonts, images, or sounds, no fetch/XHR/WebSocket. Any sound must be synthesized with WebAudio.
2. The iframe sandbox is "allow-scripts allow-pointer-lock" (plus an autoplay permission). So: no localStorage, cookies, or indexedDB (opaque origin — access throws); no popups, window.open, or navigation; no access to the parent page; alert()/prompt()/confirm() are silently blocked.
3. The playfield must be visible within 800 ms of load — that is when the screenshot is taken. No dead white screen. If there is a start screen, make it visually rich.
4. Controls: keyboard AND mouse must both work, plus on-screen touch buttons for phones. Call preventDefault() on game keys (arrows, space) so the page never scrolls.
5. The view is 16:9 and must scale to fill the viewport with no overflow or scrollbars.
6. Show a visible score. If the genre has a losing state, show a game-over screen with a restart (button and a key). Idle/clicker games skip game over but still need clear numeric feedback.
7. If you track a score, report it to the arcade shell so the player's best is remembered between visits: on every score change, call parent.postMessage({ source: "ai-arcade", type: "score", score: <number> }, "*"). It is safe to call it no matter what the parent does with it.
8. Keep it tiny: aim for under 400 lines, 60 fps, no frameworks. That 400-line target does not apply to 3D games — true 3D (a camera and perspective-projected world) or pseudo-3D (projected road/track, depth-sorted sprites) — which need their own software renderer and typically land at 800–1400 lines. The rest of this constraint still binds every game: 60 fps, no frameworks, no external assets, and no padding to reach a length.
9. Difficulty: the arcade shell passes the player's chosen difficulty as a URL query parameter. Read it with new URLSearchParams(location.search).get("difficulty") — the value is "easy", "medium", or "hard" (missing or unknown means "medium"). Make the three levels meaningfully different — speed, lives, enemy pressure, reaction time, whatever fits the genre; clicker/idle games with no losing state use starting resources and upgrade cost curves instead. Show the active level in the HUD. Without the parameter the game must be fully playable at its default (medium) tuning.

Return only the complete HTML file, no commentary.