Beam/Bullet distinctions

This somehow broke angle tweens. So that's cool!
Experimenting with property animation

Kind of just messing around right now. The Beam/Bullet distinction
throws a bit of extra complexity in there that I feel a bit queasy
about. It's tempting to have a clear divide between barrage scripts and
beam scripts, especially since beams behave fundamentally different.
Maybe new BulletBarrage and BeamBarrage types or something?