Converted Fish World to use the Playscape SDK. Key changes:
- Added `playscape.json` manifest with topdown controls for mobile joystick
- Integrated SDK for viewport handling, input combining (mobile + keyboard), pause state, and leaderboard submission
- Responsive canvas that fills entire screen using `sdk.getViewport()`
- Combined input from SDK (`getControls()`) for mobile and keyboard listeners for desktop
- Game over screen submits score to leaderboard via `sdk.submitScore()`
- Added tunables for player speed and start size

**Next Ideas:**
1. **Sound Effects** - Add underwater ambient sounds, bubble pops when eating fish, and danger music when predators are near
2. **Power-up Variety** - Add speed boost bubbles and size shrink/grow mushrooms for strategic gameplay

**Ready to level up your game? Pick one and let's build it!**