About
Galaga is a 1981 fixed shooter by Namco, the sequel to Galaxian, in which the player destroys waves of enemy ships while avoiding capture by tractor-beam-wielding 'Boss Galaga' enemies, which can be rescued to form a more powerful dual fighter. XGalaga is a Galaga clone originally written for X11 by Joe Rumsey starting in 1995 — previously distributed as shareware before being placed under the GPL — later ported to SDL by Andy Tarkinson, Frank Zago, and Dan Espen. It supports fullscreen and windowed modes, an adjustable starting level, and a configurable window size via command-line options.
Getting started
Movement uses the left/right arrow keys with the space bar to fire; 'p' pauses, 'q' quits, 's' toggles sound, and Alt+Enter toggles fullscreen. Command-line flags let you start at a given level, run windowed at a custom size, or print the high-score tables.
History
Previous versions of XGalaga were released as shareware; the author later placed it under the GPL after concluding the shareware payments weren't worth continuing.