It’s funny how Hollywood actors are usually praised for trying something completely different in their careers, while musicians are so often derided for the same thing.

Think of Laurence Olivier abandoning his noble thespian routine to play the sadistic dentist in Marathon Man, for which he was universally acclaimed. Then compare that with the panning Bob Dylan received when he decided to go electric.

Where do video games sit in all this? Well, gauge your own reaction to the news (whenever you heard it) that id was making an RPG out of its classic first-person shooter franchise Wolfenstein. Were you pleasantly surprised, or adamantly opposed? Right now it doesn’t matter what your view is, because you'll love this new iPhone version.

You may recall our review of the Java version earlier in the year (for those who don’t, we liked it to the tune of an 8 out of 10 Silver Award). What we have here is a much enhanced version, bringing with it revamped visuals, adapted controls and some quirky mini-games.

The game has you make your way through the grounds of a Nazi-infested compound (including Castle Wolfenstein itself), with the action viewed from the eyes of U.S. Special Ops agent B.J. Blazkowicz.

A few moments with the game will reveal it to be much more than a simple blaster, however. Whilst you explore the simple block-based environments in real time using a virtual D-pad, combat is of the turn-based variety.

Upon encountering an enemy you have all the time in the world to decide whether to attack (a simple tap of the screen with your chosen weapon drawn) or move to a more strategically advantageous position (a horizontal swipe on the screen activates a side-step in that direction).

You can also pause to bring up a menu, from which you can heal yourself or use one of many status-enhancing syringes to temporarily boost your stats.

Ah yes, stats. All of your actions in the game award you experience points, from combating foes to smashing up enemy artefacts. In time honoured RPG style, accruing enough XP will level you up, boosting your attacking and defensive abilities.

If talk of stats and experience points puts you off, don’t let it. While you do get a fair amount of old skool RPG information thrown your way as you advance through the game, you can happily ignore it. As long as you manage your resources fairly wisely and keep one eye on your health gauge, you’ll make fairly serene progress through the early parts of the game.

By that point you’ll have been well and truly sucked in by the game’s distinctive presentation and cheeky sense of humour.

While Wolfenstein RPG stays true to its blockily retro heritage in terms of the setting, all of the rough edges have been smoothed off. The chisel-jawed guards and ghoulish skeletons remain defiantly two-dimensional; they’ve been rendered in a brilliantly expressive style that feels wholly new, while never abandoning the Wolfenstein aesthetic.

There’s a fair amount of humour in this latest iteration, too. Look out of a window and you might see a googly-eyed chicken plummeting to its doom, while a hilarious early encounter with a bunch of guards in a bathroom led to me using the toilets as offensive weapons.

Venture into the catacombs and the spooky atmosphere is broken with some groan-inducing tombstone engravings. “Here lies an atheist, all dressed up and no place to go,” is just one example.

Wolfenstein RPG is full of such balancing acts: hardcore RPG elements rounded off by chicken-kicking mini-games. An intense tale of storming a Nazi castle set against a jokey script. And chief among them: a distinctly retro-tinged experience that feels perfectly at home on Apple’s state-of-the art iPhone. Unmissable.