Planet Arena now offers a new version 7.51 of Alien Arena 2011, COR Entertainment's freeware first-person shooter which uses an open-source game engine based on GPL id Software source code. For the unfamiliar, here is part of how the developers describe the game: "This game combines some of the very best aspects of such games as Quake III and Unreal Tournament and wraps them up with a retro alien theme, while adding tons of original ideas to make the game quite unique." The new version includes a rewrite of BSP surface rendering providing what they call a "massive" performance improvement. All the details are in this change log.