XONG is a free, fast-moving procedurally-generated puzzle combat game for Microsoft Windows, Mac OSX, and GNU/Linux. XONG is for one player and is played using a keyboard and mouse. XONG is pronounced "zong" and programmed entirely in Common Lisp.
You control a vulnerable white square attempting to infiltrate a semi-randomly generated abstract color field environment infested with robots. You are armed with a paint-absorbent hockey puck that can pick up color and transfer it to other objects. If you lose your puck, you have to find another; these are scattered through the environment and look like the letter P. There are no hit points; any hit kills you, and completely ends your game. You cannot shoot enemies; instead you drop direction-changing arrows called "chevrons" to guide them to their doom in one of XONG's many black holes. But your puck will also follow the arrows, so be careful where you fire; otherwise you'll lose it down a black hole.
To clear a level, one must defeat all the enemies and use the paint to open the coded lock that blocks the exit to the next level. The game generates boards of increasing difficulty as one clears them, and there is no win-condition at all; you just keep playing until you die.