Domino Row

Build a tiny browser game called "Domino Row".

Game spec
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A double-six dominoes parlor duel rendered on a green felt canvas: the full 28-bone set, seven to a hand, the rest face-down in the bone yard. The opening bone is the heaviest tile of the starter; play grows one horizontal row that wraps neatly into rows as it lengthens, with every tile drawn as a rounded bone with its two pip values and a divider, and the chain's open ends tracked as the only legal landing squares. Clicking (or number keys 1-9 and Q-Y) plays a fitting bone — illegal bones flash a message naming both ends; when the hand holds no bone that fits, the player draws from the yard one at a time until playable or empty, and passes when both fail. The House takes its turns on a half-second beat with difficulty-tiered choice (random, heaviest-pip greedy, or win-aware) and the same draw-or-pass rule. Emptying a hand is DOMINO and banks the losers' pip count; a fully blocked board settles by lower pips. First to the pip target — 100/150/200 by difficulty — wins the board and a click resets a fresh shuffle. Player pip score posts to the parent.

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.