Sweet game!
I made it to level 14 before I finally quit, and up until then I was having a lot of fun. I think your rotating cross in level 14 is a bit off though, as a lot of the time I would hit an invisible wall while trying to get passed the cross. Finally I figured out that there seems to be a pathway at the top that you slide through while passing through the cross. I got the key and was about to win but for some reason that invisible cross wall is right in front of the opening to the level's exit. ;(