Quench

Build a tiny browser game called "Quench".

Game spec
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A blacksmith's quench. A glowing blade comes off the forge at forging heat and you have one chance to plunge it into the oil at the right moment: too early and the edge is soft, too late and it cracks. The blade's colour is the instrument — cherry, orange, yellow, white — and it fades through those stages as it loses heat, so you read the temperature off the metal itself rather than a number. Hold Space (or the pad) to keep the blade over the coals and stoke the fire, which drives heat in fast but overshoots once you let go because the steel keeps conducting; release and the blade air-cools on the tongs, slowly at first then faster. The target is a heat band shown only as a swatch of the correct colour, plus a narrow window in the final second where the colour matches, so timing the plunge is the whole skill. Plunge with Enter or a click on the oil trough. Quenching inside the band hardens the edge and pays by how near the middle of the band you landed; outside it the blade is scrap, and three scraps ends the shift. A crack meter rises if you overshoot toward white, and a soft blade can be re-forged at the cost of the run's streak. The forge darkens and the blade loses heat faster as the shift goes on, and hard shrinks the band. Forge look: a coal fire with a white-hot core and drifting sparks, an anvil with a swage, a trough of dark oil that smokes and boils on entry, scale-flaked steel, and a hiss plus hammer ring 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.