- Implement `AlienShip.explode()` with cyan flash, shrinking spin animation and a shockwave ring.
- Enhance `Player.die()` to flash white, hide the sprite, and spawn shattering shard graphics.
- Introduce `GameScene.spawnImpactSparks()` to create brief yellow spark particles on bullet impacts.
- Update bullet‑asteroid and bullet‑alien collision handling to trigger impact sparks and use the new alien explosion.
- Minor refactor to use the new visual effects for a more polished death sequence.
Brian Fertig