Marvelous! Couldn't stop playing.
I rarely have patience for puzzle games, but this one is an exception. The learning curve is quite good, music is great and since it is different between levels it doesn't get repetitive and graphics are more than adequate (honourable mention goes to Dude, who looks adorable in a lab coat :).
The levels are designed very well, I haven't found any glitches and the arcade element (i.e. dodging monsters) gives a much needed distraction from puzzle solving.
Seriously if you have any work to do, don't play it. If you, however, can spare one hour or so - PLAY THE GAME.