UFO2000 is a multi-playable remake of
Microprose's X-COM: UFO Defense that uses
the Allegro game programming library. It can use the data files from original game, but does not require them.
Celestia is an OpenGL-based 3D space simulation for Unix and Win32 that lets you travel through the solar system, to the stars, and even beyond the galaxy. Visit over 100,000 stars, 100 solar system bodies, and all known extrasolar planets.
Falling Block Game is a block-stacking game similar
to Tetris. The timing and scoring are similar to the
original Gameboy game, but the visuals and piece
control are much improved.
Retro is a clean, minimalist language with roots in Forth. It supports all major OSes in use today, and was designed to be easy to learn, use, and modify for specific needs.