Final Approach

Build a tiny browser game called "Final Approach".

Game spec
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A flight-control arcade game in one self-contained canvas file, styled as a dark radar scope with a soft grid and three colour-coded runways (cyan left strip, amber right strip, magenta bottom strip, each with threshold ticks and a letter). Aircraft spawn at random map edges on a timer that tightens with every landing (gap = base x ramp^landed, floored), heading inward, each tinted for the runway it must reach, with a fuel ring drawn around the airframe (warning tone under 5 s). The player drags from any plane to draw a dashed polyline flight path in the plane's colour; planes steer toward waypoints with a capped turn rate (2.4 rad/s banking), consume waypoints within 12 px, and land by entering their colour-matched runway rect, paying base bonus plus 4 per second of remaining fuel. Losses: midair collision (pairwise radius check), fuel exhaustion (explosion), or wandering off radar. Every 8 landings a new 'shift' banner raises traffic. Zero clearances ends the run with a score card, landings count, localStorage best (try/catch for the sandbox) and reopen button. WebAudio for spawn blips, landing chords, crashes, off-radar, fuel warnings and shift fanfares. HUD plates show active traffic, landings, shift number, score, clearance lives and the difficulty tag; score posts via parent.postMessage({source:'ai-arcade',type:'score',score}). ?difficulty=easy|medium|hard (default medium) scales lives, spawn pressure, plane speed, fuel, collision radius and landing bonus. Attract mode flies two demo aircraft on holding circles behind the title screen, harmless by design; touch works via the same pointer-drag pathing.

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.