App Store success stories can often come from the place you least expect. The Letris series is one such success, and it's a game franchise we haven't really had our eye on. The premise is simple: it's Tetris with letters - essentially a more single-minded version of Puzzlejuice.

You create words through tapping letters, and try not to let your stack reach the top of the screen. Letris 3 is the latest in a series so popular that's it's apparently spawned its own game show, so we though it was finally time for us to see what all the fuss is about.

The simple premise offers up a surprising amount of varied gameplay. One stage will have you using letter to a set number of words. Another will have you clearing stone blocks by using the letters adjacent to them, and yet another will require you to survive for a set period of time. The tap controls are easy to master, and in terms of engagement, the consistently rising screen creates a tension that never dulls no matter the circumstance.

What ultimately detracts from this tension, however, is the game's freemium design. Each stage will consume one of your Letris tiles, of which you only have a limited amount. You can gain more for achieving at least two stars upon completion, but if you run out (by, let's say, failing at a particularly difficult stage), you will have to either wait for the tiles to be refilled, or pay for more.

In many word games, despite the imposed time limit or rule set, you are always trying your hardest to create the largest words you can find. But here, conscious of the fact you might not be able to try again till later you'll find yourself tapping any three letter word you can find in order to satisfy the base objectives and get your two stars.

So, even with the clever boss monsters and multiple modes (plus tournaments where you can win prizes), Letris 3 seems more concerned with leeching that letter wrangling. While there is an engaging and adept word game underneath these trappings, the freemium setup is not doing the game any favours. We recommend trying to find episodes of the televised game show instead.