Bungie's pre-Halo FPS Classic Marathon Infinity just launched on Steam for free, meaning you can now play the entire Marathon trilogy for the low price of nothing

The player is surrounded by alien enemies in Classic Marathon Infinity.

Old timey FPS Classic Marathon Infinity has just landed on Steam, meaning you can now play all three Classic Marathon games via Valve's distribution service for free.

Originally released in 1996 (without the word 'Classic' in its title) Marathon Infinity was the last and largest game in Bungie's pre-Halo FPS series. Its "Blood Tides of Lh'owon" campaign, which could be played either solo or cooperatively, offered 20 levels that included new enemies to fight and weapons to fight them with, as any FPS sequel demands.