It seems likely that some of you will not be aware of ’90s classic Marathon, which was one of those obscure-yet-influential games in the history of the shooter. It was one of the things Bungie did before they really made hay with the Halo games. Anyway, fans have continued the series, as well as powered a number of other games, with an open-source engine-creating effort called Aleph One, and that project recently hit a big old milestone, v1.0. This means it’s a good time to download one of the games related to the project if you are looking for some retro FPS adventures. Needless to say there are Mac OS X, Windows, and Linux versions.