It's a defining moment for id Software and its iPhone campaign.
As great as its back catalogue role-playing, turn-based reinventions have been, they're hardly a new concept any more.
The events of Doom, when a Mars station opened up to the legions of hell, have been covered up, and a new team has been dispatched to find out what's going on. The game begins as you touch down at a halfway house on the moon, only to find there's trouble afoot there too.
Doom II RPG launches you straight into the action as one of three characters - a female marine, a male marine, or a scientist with milk bottle bottom and NHS glasses. Each has his own tweak on the skill statistics, though there isn't a huge difference made to the gameplay after making your choice.
You're not kept waiting long before the monsters attack, and that's a real strength of Doom II RPG. Were it to linger, you'd have the chance to realise that it really isn't any different from its predecessor. The constant stream of action plasters nicely over that particular crack.
The core of the game is spent chasing down the portal to hell, winding through a labyrinth of futuristic levels with aliens, demons, and zombies around every corner. Basic puzzles break up the journey as you hunt down key cards to get through locked doors, activate obstructive computers, and hack into the mainframe.
A selection of NPCs pop up at intervals to keep you posted on what's going on, but for the most part you'll be occupied with searching for new weapons, hidden rooms and ultimately, the way to hell (and back).
Nothing that's immensely challenging, but the size and complexity of the maps is more than enough meat for the gameplay gravy.
Highway to hell
Touchscreen controls have rarely fared well on iPhone first-person shooters, but luckily for Doom II RPG this isn't strictly an FPS (as its name suggests). The movements are made with a simple on-screen D-pad, with left and right rotating you 90 degrees in that direction.
Strafing is accomplished by swiping the screen, so finding your way around the levels is very easy and immediately accessible.
Everything else is controlled by a quick touch, whether swapping between the Super Shotgun, BFG or even the new Holy Water Pistol, or sticking your chainsaw into someone's ribs. Again, it's very easy and intuitive.
Fighting is handled using a turn-based system rather than a bullets-out firefight. This combat system takes a lot of strain off the movement, allowing you to find your virtual buttons in your own time and to make decisions on whether to move, shoot, skip a turn, or change weapons.
It wouldn't work as well on a different platform, but for the mobile devices the RPG element is crucial to the enjoyment.
Hell and back again
All the wry humour, functional 3D visuals, variety of characters, and non-stop action plot are all present in Doom II RPG, but ultimately this feels much the same as the previous id Software RPG retro outings.
Even new enemies such as Sawcubus and Sentinel, alongside Cacodemon, Revenant, the Cyberdemon, and Spider Mastermind aren't testament to radical progress.
If you have a particular fondness for Doom II then you're likely to pressing the 'buy' button anyway, and won't be disappointed. But if you've already shelled out for one of id's recent iPhone re-releases, the lack of new gameplay elements will make it feel overly familiar.
Still Doom II RPG is an enjoyable romp so don't be put off if you're feeling curious. Just be aware that, like the PC original, this is essentially more Doom and less innovation.