Mike Mulligan and His Steam Shovel Opposites Game

"The object of all three games [Beginner's, Advanced, and Memory] is to match two puzzle pieces -- opposites -- and fit them together to make a pair. Need help? Each puzzle piece is specially cut so it only fits one piece -- the opposite that matches it. That's why we call this a self-correcting game. You don't need a grown-up to tell you if it's right. If the pieces don't fit, you know you need to try again!" Based on the book by Virginia Lee Burton.