SimMars is a mod for SimCity 4 taking the game to Mars. It will bring new buildings, transportation systems, user-interface and music and will replace the Maxis SimCity 4 content as far as possible, giving you the feeling to play a colony on Mars. The mod is still at beta stage. Beta 3 was released in October 2010.
Downloading and installing was easy, and building my first colony was a blast. Sure, there were a few erroneous things about but it was a beta, those are to be expected. I saved and exited, and when I tried to play it a second time it said that a certain folder didn't exist, despite the fact that yes, it did exist. Then I tried to play regular SC4, only to find the SimMars interface on it! I want to be able to play SC4 and SimMars separately, and without folder ********. The game itself is good, but I myself am going to wait until Beta 4 for another go. Let’s hope they fix these two issues by then.