Closure is now available on Mac and Windows via Steam (previously on PS3). If you like platform puzzle games, or if you like games that play with the nature of the virtual universe, then you need to play this game. Convinced my description is inadequate for a purchase decision? Play the free Flash original.
I bought it as soon as it came out and while I haven't finished it, I've played through several of the puzzles and it is living up to what I'd hoped it would be. The one thing that bothers me a bit is the loss of the original version's 1-bit aesthetic. (Yes, I said 1-bit, not 8-bit. I'm talking about color depth, not word size.)