Doptrix is Tetris inverted. It's a brain-blendingly ingenious puzzler in which you can't rotate the pieces, but you can rotate the board. Spin it clockwise or anti-clockwise, flip it head over heels or side-to-side: re-position the playing area as much as you want, in fact, and then fire your tetromino onto it. Done. The basic rules keep in step with Alexei Pajitnov's world-beating masterpiece - construct unbroken lines in order to clear them - but everything else about Doptrix is weird and disorientating. Familiarity has never felt so unfamiliar.
It's a bit like learning a new language, in fact: there are unifying structures that you can cling to when you spot them, but they're buried beneath a wealth of new ideas, and they only peek out every now and then. That's at first, anyway. I think Doptrix takes half an hour or so to truly bed itself into your brain. You can tell it's a brilliant idea within seconds, but only after a little time has passed are you actually having any fun.
In order to work, Doptrix divides its screens into two different areas: the top area is the game grid, and this is the part you can spin around and flip with a couple of swipes of a finger. Beneath that, you have a kind of launching pad - a board that shows you your current piece and the ghosted outline of the next one that's coming down the pipe - that allows you to flick each block to move it up into play.