Sweep Strike

Build a tiny browser game called "Sweep Strike".

Game spec
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A side-view curling match against a CPU skipper on a single sheet, thrown left to right at a four-ring house. THE PROMISE: one velocity — the orange aim arrow and the dashed predicted-stop circle are computed from the same v and friction the integrator consumes (stop distance = v^2 / 2F), so the marker on screen cannot lie about where the stone rests; an in-file self-check integrates the real physics and fails if the marker drifts more than 12 px, and demands a full pull can actually reach the button. Drag back from the hack to set weight and line (line clamped to +/-0.42 rad); release to throw. While your stone glides, hold Space, click, or touch to sweep: friction drops to 45% in the marked running lane only, and only for your own stone — sweeping is the game's one live decision after release. Equal-mass near-elastic stone collisions let you guard and take out; a stone over the back line is dead. The CPU solves the same physics backwards (v = sqrt(2Fd)) to stop on the button, and switches to a takeout line — aimed 12% past your shot stone — when you hold it, so holding the button is never safe. Scoring is real curling: only the team holding the button scores, one point per stone beating the best opponent stone, blank ends allowed, hammer alternates, and draws go to the far end. Difficulty scales ends (2/3/4) and the CPU's weight/line error. Score reported via postMessage; audio synthesised in-file; no external requests.

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.