This game is beautiful and very creative (beautifully simple =P). I loved it!
A hint to newbies trying the game: You can press space bar at any time to go back to the puzzle screen.
I don't know why but in the earlier stages I thought I was just stuck after pressing space bar once haha.
Ok so level 13, a good fix would be to either not have the dragon cannon at all, or have the centre blue bouncy.. circle thing... go up further so you can fall past it.