Tell me one thing - did you personally win all the levels you designed? If so, then I wonder how did you manage to fit in those 8 hours. ;)
Just one thing I found quite annoying - the level restarts when you touch the left side of a tile. Sometimes you don't even fall down, but the screen suddenly fades. Maybe it's intentional, but still...
I know it's meant to be impossible, but there should be at least hard/easy mode (or 2-3 easier levels), or some not-very-tireless players will rage-quit soon and give you bad rating.
Congratulations on your first game. ;)