Following the release of Doom 3, many speculated what project its creator John Carmack would take on next. However, few would have guessed that project would be...a mobile phone game? As unlikely as that may sound, apparently a mobile game is what the cash-flush cofounder of id Software and the would-be astronaut is currently working on.

In his latest blog entry, Carmack talks about how a chance occurrence caused him to become interested in making mobile games. "A little while ago I misplaced the old phone I usually take to [Carmack's rocket company] Armadillo [Aerospace], and my wife picked up a more modern one for me. It had a nice color screen and a bunch of bad java game demos on it. The bad java games did it... So, for the past month or so I have been spending about a day a week on cell phone development."

After explaining his motivation, Carmack then outlined the mobile platform's limitations. "You aren't going to be able to make an immersive experience on a 2-inch screen, no matter what the graphics look like," he said "Moody and atmospheric are pretty much out. Stylish and fun is about the best you can do."

Carmack continued, "The standard cell phone-style discrete button direction pad with a center action button is a good interface for one-handed navigation and selection, but it sucks for games, where you really want a Game Boy-style rocking direction pad for one thumb and a couple separate action buttons for the other thumb." He then came to the conclusion that "the majority of traditional action games just don't work well with cell phone-style input."

So what kind of game is Carmack making for mobile phones? How about a first-person role-playing game set in the Doom universe? "What I decided to work on is DoomRPG--sort of Bard's Tale meets Doom," he said. "Step-based smooth-sliding/turning-tile movement and combat works out well for the phone input buttons, and exploring a 3D world through the cell phone window is pretty neat."

According to Carmack, the Doom RPG is being developed by Fountainhead Entertainment, most famous for its machinima shorts, and will likely be published by Jamdat. He expressed some frustration with the various phone platforms' eccentricities. "We are only testing on four platforms right now, and not a single pair has the exact same quirks. All the commercial games are tweaked and compiled individually for each (often 100-plus) platform. Portability is not a justification for the awful performance."

Speaking of awful, Carmack also complained at length about the J2ME Java programming language. "The biggest problem is that Java is really slow," he said. "On a pure cpu/memory/display/communications level, most modern cell phones should be considerably better gaming platforms than a Game Boy Advance. With Java, on most phones you are left with about the CPU power of an original 4.77 MHz IBM PC, and lousy control over everything."

GameSpot will have more on the mobile Doom RPG as further details emerge.