A fun game just released for Mac users out there. Enigmo 2 is one of those simple-concept, difficult-execution games.
You have to use mirrors, magnetospheres (yes), guttering, etc., to get water drops, laser beams or plasma (yes) from the source to a defined finish point. Starts simple, but there are 50 levels of rapidly increasing fiendishness. Fantastic graphics, and appropriately noodly new age music.
Free demo available, and trailers, via the link above.