Particles and collisions of joy!

I fixed the collision detection.  Rather than trying to be smart, I just went for the brute force method.  Turns out, when you have less than several thousand objects to consider, it doesn't really matter...

Also, added a particle system.  Need to add stuff like tracers, but that will be a piece of cake now.

And, there's now a status bar at the top of the screen.  Shows how many lives you have, what level it is, your score and the number of super-weapons left.  Hasn't been fully implemented, so more on that later...