Invaders now only shoot if they are in the front.
Introduced SpriteObject class, made it superclass of Ship. Fixed ship movement restriction.
Made Ship, Bullet subclasses of SpriteObject. Fixed animation code in SpriteObject.
Switched to JDK 6 due to strange bugs
Collision now handled by individual objects
Switched to JDK 6 due to strange bugs
Merge branch 'master' of horibe:progra-invaders
Bunkers are no destructible
Pretty death animation for invaders
Removed old code in Bullet.update.