Implement wave-based enemy system with shooting enemies, improved visuals, and sound effects
- Added enemy bullet system with dedicated group and canvas texture
- Implemented wave progression system (3 waves) with increasing difficulty
- Enhanced enemy spawning with wave-specific properties and shooting mechanics
- Added player explosion animation on death with sound effect
- Included wave start notifications with scaling text animation
- Improved background scrolling and enemy off-screen cleanup
- Integrated new sound assets for enemy shooting, player death, and wave transitions
- Updated game scene with proper texture handling for different enemy types across waves
This commit transforms the basic shooter into a structured wave-based gameplay experience with escalating challenge levels.
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