Aspyr has released a free demo version of its cult game, DOOM 3.

"The ruins of an ancient Martian civilization have unlocked the secrets to teleportation, and the UAC will stop at nothing to harness this world-altering technology. As part of a marine detachment sent to protect the facility, your duty seemed simple enough…until the invasion."

"DOOM 3's dramatic storyline, pulse-pounding action, and incredible graphics, combine to produce the most frightening and gripping gaming experience ever created," Aspyr says.

The demo lets users play through the first chapter of the game. It includes three levels. The 463MB download is available now.

System requirements: Mac OS X 10.3.8; a G4 or G5 processor at 1.5GHz or faster; 512MB RAM; 2GB disk space; recent video card.