Lasers, rockets, shields, health regeneration, pixels. You know. The good stuff. Just nicely packaged with levels of just the right duration and hardness, persistent upgrades, shaders, reverb...
Two buttons are enough to play, since that was one of the themes of Ludum Dare #34, in which the game came #74 among 1638 jam entries.
Supser Space Invader was made with LÖVE (v0.9) and thus runs on Linux, OS X, Windows.
The source is available on GitHub under zlib/libpng.