Cheap design teams have been cloning Tetris for years - there's just been an interesting court case regarding a prominent copycat, in fact - but more interesting developers have also been experimenting with it. Whether they're just changing the dimensions of the well and altering the shapes of the blocks or going so far as to add new power-ups and meddle with the basic rules, you don't have to hunt around the internet for too long to see Alexei Pajitnov's evergreen classic getting a bit of a workout.
Android owners already have Doptrix to mess about with when they're in the mood for a Tetris variant, and now they've got Block Quest, too. Block Quest is rough around the edges and saddled with a rather naff UI, but there's something completely brilliant lurking at its core - something that could really start to shine after a few more updates from the developer, perhaps.
The elevator pitch is brilliant: imagine Tetris spliced together with a dungeon crawler. It's simple, really. The pieces you're arranging in the well aren't blocks so much as sections of floor tiles, and you're stringing them together to create a complex environment for your auto-roving adventurer to navigate. Red edges on a block mean that it will count as a doorway, connecting two pieces when you set it in place, while the squares themselves might be filled with monsters to battle, crystals to heal you, or - finally! Yes! - the stairs down to the next level.