RetroVaders is a freeware "tribute" to Space Invaders, released for Linux, Windows and MacOS X.

In case anyone hasn't ever played space invaders before (anyone?) the game is played as follows: shoot the aliens before they reach the bottom of the screen. Shoot bonus UFOs for extra points, hide behind or shoot through the bunkers, avoid getting shot.

License: free

Additional System Requirements: Requires libsdtc++.so.6 or higher and a hardware accelerated X server.