id Software Lead Engineer/designer and legend John Carmack has confirmed in a recent interview that the single-player game of Doom 4 at 30 frames per second (FPS) is running. The multiplayer part, however, would run at a constant 60 FPS. "In multiplayer mode of Doom 4, we have opted for 60 frames per second. In single-player mode, however, Doom 4 runs in 30 FPS. Accordingly, can you fight against twice as many monsters," says Carmack. Deeper detail was not mentioned by Carmack.