Download for Windows (31MB)
Download for OSX (37MB)
Download Source Code (Unity 3)
edit: uploaded a newer version, fixing some graphical and sound glitches, as well as a bug with one of the puzzles (that would render it either trivially solvable, or unsolvable if you went to night and back).
edit: uploaded a newer version still, fixing a couple of game logic bugs.
[ thanks to perrin, mcc, alex, and rico for testing : ) ]