Trism is an affordable and fun puzzle game now available for the Apple iPhone and iPod Touch. It costs £2.99 in the UK, and $4.99 in the US, depending on which version of the iTunes Application Store you're on.

Trism has much in common with Tetris, Bejeweled and various other currently popular puzzle games, but with an interesting twist. The whole game is based around triangular tiles, which must be grouped as three or more of the same colour. To do this, the player can slide entire rows of triangles along in any of six directions - the triangles are equilateral, so you can probably imagine how this works. When the tiles are clustered in groups of three or more, they will disappear and new tiles will slide into place. The great bit, however, is that when the new tiles slide onto the screen, they fall according to gravity - basically, you hold your iPhone or iPod whichever way up you like, and the tiles fall in from the top edge, along one of those six axes.

You probably have a vague idea in your head right now, so the best thing to do is pop along to YouTube and hunt for 'Trism' - there are one or two gameplay videos on there which make it all much, much clearer than any amount of description can. As with many of the new iPod/iPhone games, the accelerometers in the device are allowing for unique and new styles of gameplay.

Trism features interactive tutorials, three different game modes, including one which is played solely by tilting the device, and (best of all) a colour blind-friendly mode. This adds letters to the tiles, which is essential for me as I can't tell any difference between the blue and violet tiles. There are little animated screws which occasionally pop up to fix a tile in place, effectively stopping three rows of tiles from sliding. There are bomb tiles which need to be disposed of within a certain number of moves, and special rainbow tiles which help you set up excitingly gratifying combos. Great reviews and feedback, so even though, as of writing this node, the application is only at version 1.0 there are already plenty of improvements planned in the Trism online forum. An online high score table lets you compare yourself to other mobile time-wasters, as well.

My recommendation? It looks great, sounds good and plays well - if you're wondering whether to splash out the price of a pint of beer on an iPhone app, don't hesitate.

Trism is published by Demiforce, LLC. Their homepage is here, or you could visit the Trism Forum.