Done! I've made the following improvements:

**Arena Changes:**
- Increased canvas from 800x600 to 1200x800
- Default arena size from 300x300 to 600x600
- Added arena size selector: Small (400), Medium (600), Large (800), Huge (1000)

**New Options:**
- Fighter speed multiplier (0.5x - 3x)
- Particle quality settings (Off/Low/Medium/High)
- Win condition selector (5/10/15 hits)
- Reset game button

**Performance Optimizations:**
- Canvas context with `alpha: false` and `desynchronized: true`
- Particles use `fillRect` instead of `arc` (faster)
- Particle draw/update separated for better cache locality
- Particles only process when quality > 0
- Particle decay increased from 0.02 to 0.03 (shorter lifespan)
- Dynamic particle counts based on quality setting
- Game state checks prevent unnecessary calculations

**Next Ideas:**
1. **Add Obstacles** - Place pillars, walls, or moving hazards in the arena that fighters must navigate around
2. **Power-Up Drops** - Random items appear that grant temporary speed boosts, shields, or weapon enhancements

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