id Software's second game for the iPhone and iPod Touch comes in the form of a new Doom installment.

Although posted on June 26, id Software's Doom Resurrection finally became available on iTunes earlier today. Unlike id's slick port of its infamous FPS Wolfenstein, Doom Resurrection is an entirely new game built especially for the iPhone and iPod Touch. Weighing roughly 80 MB, the $10 game only offers eight levels-- six on Mars and two in Hell--all of which pull straight from 2004's Doom III assets and concepts rather than the pixilated, older (yet classic) installments. In fact, the game sports a level of detail 'one level down' from the original PC game's resolution, and frankly looks and flows fantastic.

Developed by Escalation Studios under id Software's supervision, the storyline runs in parallel with Doom III: scientists in a remote Mars facility have lost control of their experiment and all hell (literally) breaks loose. The player assumes the role of the last survivor of a group of marines originally sent in to investigate the accident. Naturally, the task at hand is to save the scientists, and to discover a way to stop the infernal invasion using an impressive arsenal of weapons. According to this interview, Doom Resurrection's setting actually takes place in a different part of Doom III's facility.

Unlike most FPS games currently available on the iPhone and iPod Touch, the game takes Doom in a different direction and removes free-roaming gameplay. This may disappoint many die-hard Doom fans, but previous FPS titles on the iPhone and iPod Touch have proven to be more difficult in mastering the touch screen controls rather than any difficulty settings the game may provide. With that said, Escalation and id chose to throw the player on 'rails,' pre-scripting the game's progression while providing 'free-look' controls to the player.

Does it work? This type of gameplay certainly puts the focus on the experience, however ultimately whether the railing flies or dies depends on the individual preference. Doom Resurrection takes advantage of the device's accelerometer: tilting forward moves the aiming cursor upwards, tilting to the left moves the cursor to the left. Thus, the simplified schematic provides a limited set of on-screen controls including a situational dodge button, a fire button, and a weapon switch button.

Earlier this month, id Software's John Carmack said that the current aiming mechanism wasn't the first version implemented into Doom Resurrection, that the game originally featured a 'Whack-a-mole,' tap-to-shoot mechanic. 'Tapping is actually too efficient of a control mechanism,' he told Slide to Play. 'It felt like a productivity app. There was no tension, and you couldn't see the damage animation on whatever you were shooting at because your finger was in the way. But the game really turned the corner when we put in the new aiming mechanism.'

For now, Doom Resurrection only offers the eight-level single-player campaign, however downloadable content and bluetooth-enabled multiplayer are planned for future updates (free-roam patch perhaps?). id Software also announced that the original Doom (Classic) title is getting ready to hit iTunes as well, supporting OS 3.0 along with bluetooth multiplayer and additional downloads.