The plot of the game is similar to that of Doom 3, but it takes place in a different part of the space station than the Doom 3 story. You are the sole Marine survivor on a remote research facility on Mars where all hell has broken loose in the form of demons from hell. Hence, its a completely original game in that sense. Players can talk with scientist characters in the game. And they can use all of the same weapons and fight the same monsters as in Doom 3.
The game has eight full levels and about five hours of game play. The team expects to be able to use various iPhone software 3.0 features once they are released, but Carmack said the game was built to run fine on the current iPhone operating system. The game runs at 30 frames per second on the latest iPod Touch, and perhaps half that speed on the earliest iPhone handsets.