Taking shape

It's been a while! This build has:

- Programmer art
- Better feeling ship acceleration/inertia
- A theoretically-working second player
- A super terrible AI if there's only one controller attached
- Sounds
- Particles
- A lot less random squares

Next on the list is polishing up the bullets, tweaking the AI, and finding a way to prepare a windows build so that I can have folks test this out.