- Replaced simple circle/rectangle graphics with a spritesheet-based player sprite.
- Added animation definitions for idle, walk, idle-gun, and walk-gun states.
- Implemented state tracking (`_isMoving`, `_isShooting`) to drive animation switching.
- Adjusted barrel position calculation to use `GUN_TIP_DIST` for bullet spawning.
- Updated invincibility tween and cleanup logic to target the new sprite object.
- Added sprite loading in GameScene preload phase.
Brian Fertig