Physics:
- Set world gravity to 0; the Dino now owns its gravity (BASE_GRAVITY
2600) for a fully predictable, consistent jump arc.
- Raise jump velocity to -1180 and drop the speed penalty that made
faster runs jump lower.
- Space level now adjusts dino gravity directly instead of toggling
world gravity.
Jump feel:
- Real long/short hop via a -820 release cutoff (short tap still clears
small cacti, full hold reaches the tall arc).
- Longer coyote/buffer windows (110/150ms).
- Speed-drop kills upward momentum and pulls down at 2.2x gravity so a
jump can be cut short and chained into a duck/jump.
Obstacles:
- Widen gap coefficients (Easy 1.0->1.4, Medium 0.6->1.0, Hard
0.45->0.8) and add a hard minimum-spacing floor so obstacles can never
spawn unjumpably close at high speed.
- Spawn flying obstacles in two clear duck/run bands.
- Remove the 3-wide cactus wall from Easy mode.
Hitboxes:
- Tighten the dino body and trim obstacle hitboxes more horizontally
than vertically to remove unfair corner-clip deaths.
Power-ups:
- Spawn power-ups in a high band above cactus height so grabbing one
(e.g. slow-motion) no longer drops the player onto an obstacle.
Pause:
- Add a "Quit to Menu" button (EN + zh-hans) wired to keyboard, gamepad
cancel, and click, which cleanly tears down the scene.