Bungie's original landmark FPS Marathon is now free on Steam
Halo and Destiny developers Bungie have released their classic shooter Marathon for free on Steam, with sequels Marathon 2 and Marathon Infinity to follow. The Steam ports are the work of the celebrated Aleph One community developers, who've kept Bungie's old Marathon 2 game engine going as an open source project - and who still have PC ports of all three games available on their own site, if you'd rather not truck with Steam.