Not bad
Biggest complaints: A. The music got really annoying after a nice long while of playing (I know I could mute it but it's just not the same as a little variety). B. Kinda on the boring side.
Now that that's out of the way. Even though I said it was boring, it was strangely addicting. Fo some reason I was compelled to play the game to completion. So you obviously have done something right with this game. The controls are responsive and the puzzles were very interesting. It was a relatively easy game and I found myself passing nearly every stage well under par on the first run through.
As for the music, it was fine at first, it was just that the same 50 second song for 30 minutes gets a little old. A couple more may have softend the effect. Perhaps a song per double doors or something.
All in all, it's not really the type of game that would normally keep me glued to it like I was, so I gave it a 9/10. Possibly as much out of the mystery of why I enjoyed it as much as I did as to the actual game itself. Nice game and keep up the good work.