Vertical Platformer With Tuned Jump Physics

Create a single-file HTML5 vertical platformer (doodle-jump style) with physics that feel genuinely good. All code inline, no assets, no libraries.

Physics spec (tune around these):
- Internal resolution 960x540, letterboxed, 60fps with delta-time.
- Gravity, jump impulse and terminal velocity tuned so a full jump takes roughly 0.6-0.75 seconds and clears ~1.6 platform heights. Expose gravity and jump strength as named constants at the top of the script so they are easy to tweak.
- The player auto-bounces when landing on a platform; horizontal control via arrow keys AND touch (hold left/right half of the screen).
- Coyote time (jump allowed ~90ms after leaving a ledge) and buffered jumps (~120ms) are REQUIRED — implement them explicitly.
- Camera scrolls up as the player climbs; falling below the bottom of the screen = game over, with instant restart.
- Platforms: static, moving and fragile (break after one bounce) mixed; spawn density constant; score = height climbed.
- Player wrap-around horizontally when leaving one side (classic doodle rule).
- Game feel: squash-and-stretch on bounce, dust particles, platform fade-in from above.

After the code, print the physics constants block and explain in two sentences how to make the jump floatier vs snappier.

Fixed tuning numbers to start from: gravity 2400 px/s², jump impulse 800 px/s, terminal velocity 1000 px/s.