A mix of the arcade classics "Spacewar!" and "Asteroids" for the 18th gm(48).
Control with [W], [A], [D], [Spacebar], and with [F] for fullscreen and [M] for mute.
Hold [W] to shoot. Don't be, like, that one guy who gets flustered when pressing [W] doesn't do anything immediately.
Inspired by the combat of Frontier: Elite 2 and with the music of opengameart.com's SubspaceAudio.