What is the point of the question mark spaces? It just makes it so that you have to guess at random which isn't very fun. Without those it would be 4/5 for sure, very promising.
EDIT: I figured out what they're related to, some form of explanation of that would be appreciated so that it isn't as confusing the first time around. I'll also add though that it's still extremely luck-based whether or not you can clear the board or not.