Two things stand out while playing Marathon: Durandal, Freeverse's enhanced port of Bungie's pre-Halo PC game. First and foremost, it has just as much charm as id's classic Doom, with hilariously bad pre-rendered enemies, a fresh feeling of exploration and multiplayer options galore, both off-line and through Xbox Live. The second is a rapid frame rate that induces motion sickness. This precursor to Halo still warrants a look, especially for those who never played the original. Just remember to bring your barf bag.