Detecting collisions

We don't need to detect everything bumping into everything else. Specifically, we need to detect the following three cases:

• An alien bumping into the player, resulting in losing a life
• The alien laser bumping into the player, resulting in losing a life
• The player's laser bumping into an alien, resulting in the score going up, a particle effect explosion being started, and the dead alien being respawned

In the update method of the PhysicsEngine class, change the return statement as highlighted next:

// This signature and much more will change later in the project
boolean update(long fps, ArrayList<GameObject> objects,
                  GameState gs, SoundEngine se,
                  ParticleSystem ps){
     // Update all the...