Mobile-First Touch Controls Retrofit

You will retrofit full mobile touch support into an existing HTML5 game. I will paste the current code after these requirements — do not rewrite the game logic unless necessary.

Requirements for the touch layer:
- Use Pointer Events (pointerdown/move/up/cancel) uniformly for touch and mouse; set touch-action: none on the canvas to stop scroll/zoom interference.
- Control scheme: [choose one: "hold left/right halves of the screen to steer", "tap anywhere to jump/act, with swipe up reserved for pause", "drag to move horizontally, following the finger with slight smoothing"].
- Multi-touch safe: track pointer IDs properly; two fingers must not double-fire actions.
- 44px minimum effective touch targets for any on-screen buttons; draw simple canvas buttons for pause/restart if needed.
- No hover-dependent input: everything must work without a cursor.
- Prevent double-tap zoom and pull-to-refresh via meta viewport and CSS overscroll-behavior.
- Keep desktop keyboard controls working; the two input paths must never conflict.
- Handle orientation changes and resize without breaking the letterboxed layout.

Output: the full updated file with the touch layer integrated, then a short checklist of manual tests on a real phone (thumb reach, accidental input, pause reachable).