Stumbling Blocks is a brilliant puzzle that I've been wanting to make for a while. When Pit mentioned that he had a more difficult version I jumped at the chance to make it. Packing the four pieces into the frame is the goal, and the way to get there is amazing. I can't tell much about this puzzle without giving things away, but I'll say that it has one of the best "Ah-ha!" moments I've seen for a while. The movement of the pieces is beautiful and this puzzle rates incredibly high in overall satisfaction.