Fun guessing game. On Level 10 I got stuck right in front of the door and couldn't get out again, to search the ghost. Maybe a Reset Button would help for this case ^^. And I agree with acornellier in terms of the "rewarding" part. Maybe there could be a light switch at the door, and when you turn it off the blocks shortly appear and there is a limit as to how often can you switch it on to see where to blocks really are, or something like that :). Overall I liked it and played through all the levels!