We've seen logo recognition games, we've seen general knowledge quizzes, but this is a mash-up between the two, essentially providing a visual clue and a pool of letters, from which you have to pluck the right name, whether it's a person, a place, a brand, and so on. It's deliberately difficult though - making for a tough challenge if you want to play for free or an expensive experience if you want to buy your way through all the hints to a high score.

From the Store description:

What in the world is that???? The addictive smash hit game where you guess hundreds of celebrities, characters, logos, and more!

• Compete with your friends
• Get extra hints for correct answers
• Share your scores with your friends through Facebook
• Advance through levels as your skills improve

The walkthrough here will give you a feel for 'What in the World?':

The game is fully Xbox Live-compatible, letting you build up achievements as you go. Thankfully you can keep skipping images that you can't solve - as far as I can see there aren't any penalties, other than seeing more interstitial ads. But, obviously, you only build up your score if you solve an image. And you also have to solve half the puzzles in each 'level' of 55 in order to unlock the next one, so you have to at least try...!

Tap on letters to add them in the right order and you're done, in theory. The two green help buttons on the right reveal letters in the answer and delete unnecessary letters from the pool, respectively. As you answer correctly, you also start to build up bonus reveals and deletes.

The images are often tougher to solve though - maybe it's just me, but I was struggling for some of the sketched faces. The two above are supposed to be Rihanna and Tom Cruise, and I got there in the end, but many are just indecipherable. Still there's always the option to skip or buy some help, which seems fair enough.

Buying help can work out pricey, though an average purchase of 30 'reveals' for £2.69 (in the UK) should keep the average player going for an hour of gameplay, depending on how clued up they are.... (right) there's an attempt to bolt on Cortana support, but this is a bit clumsy. More successful is simply tapping the microphone icon to say the answer to a puzzle, though understandably this struggles with some names, brands and so on.

Over 250 puzzles across five levels should mean several hours of gameplay in all, more if you get stuck a lot.

Nicely crafted with a bright, colourful interface, you can grab What in the World? in the Store in the usual way. What do you think of the freemium balance here?