Cause everybody has to do a Boids implementation at least once. I tried to do it in a more physically accurate way (by not locking the velocity and setting steering angles, and instead actually calculating it based on applied forces).
If you decrease the size of the Byurds and apply big forces, they sometimes get stuck at the top left of the screen and can't escape. This is due to some weird interaction of overflows (maybe from air resistance squaring the velocity?). It could probably be patched with some max velocity hack or something, but not really worth the bother (also I worry that the fix would result in another bug, whose fix would result in another bug, etc., etc.).