I spent some time on a puzzle level involving nothing but sun and moon blocks the other night. I'm not really sure how hard it is, and some things definitely ought to be possible in several ways, but there are a few elements that if you don't figure out how to do them right, you're sunk. Also, if you're wondering about the blocks in the corners, they are there because otherwise the game ends (I *think* because there aren't three or more of the sun and moon blocks a piece, which normally shouldn't matter for them given how you make matches with them), telling me I lost before I'm done even though I can actually win. Delete them and try it, it's pretty odd. The ones in the middle are just there because it looked interesting to me.
Anyway, I hope someone gets some fun from it.