When we first fired up Threes!, we admit that we weren't quite prepared for the charm offensive we were about to receive.

A quick tutorial shows you the basics. To play, you must swipe a group of tiles up, down, left, or right across a 4x4 grid. Pushing a 1 tile against a 2 tile creates a 3 tile. But from there tiles only combine with tiles bearing a matching number - 3 tiles combine with other 3 tiles into 6 tiles, 6s into 12s, and so on.

The aim  of the game is to combine highly numbered tiles together to boost your highscore before the grid fills up completely.

Things quickly start to get tricky, however. Swiping left will shift every tile in that row one space to the left. When moved, the tiles will either fill gaps, or combine with other tiles 

After each move, a new tile is added to the grid. With only 16 squares available on the grid, you have to make sure that you are regularly merging tiles, and planning future combinations to ensure the screen doesn't fill up too soon.

Herein lies the challenge. While you know that you should be focusing on making sure that you don't swipe yourself into a corner, all you want to do is try to combine the highest numbered tiles to boost your high-score.

Filling the grid and leaving no possible moves left will end your run, something which is almost always a result of your own shortsightedness. Sometimes, however, the value of the random tiles that appear after each swipe can throw a spanner in works. An unlucky number tile can easily stump you, and end a game despite you carefully-laid plans, something which can prove maddening at times.

Despite the frustration this can cause, the game still manages to keep things upbeat. Each of the blocks has its own face and personality, complete with a silly voice and back-story, giving the game a welcoming, jovial tone.

Elegant in its simplicity, but punishing in its challege, Threes! is a beautiful little package. Though there's a random element that holds it back from true greatness, we reckon you'll find yourself hooked on this mathematical brainteaser in three minutes flat.