Now I love puzzles and since we're home I got this for my stepdad and niece to build together. They said that most every piece fits into each other. The only way for them to know if they have it correctly is to turn it over and make sure both pieces have A, B, or C. This takes all the fun out of a puzzle. It's no fun when you have to separate the pieces first. After having to separate from the back letters they gave up and put it away. My mom is just going to donate it.