Michael "Brog' Brough, the cleverbrain behind Glitch Tanks and Vertex Dispenser, has gone and made a free puzzle game for you and me, on Mac or PC. It's called Corrypt, and it's got one of those simple game mechanics that grows up through the levels to produce brain-curdling complexity as you go on. Nor is it simply about puzzling - there's a map to explore, and creatures to encounter and help out with their woes. As is typical with Brog's work, it is lo-fi and beautifully conceived.
And even there's even Some Noise. (Which made me laugh out loud.) Go play it.