13 pieces puzzle

The goal is fit all 13 pieces into the frame. It's very hard. However, if you are smart enough, you can tell the two sides of the pieces. For now, it's the correct sides already. If you want to make it harder, I suggest you flip some random pieces to print. Original idea come from https://www.puzzlemaster.ca/browse/novelty/packing/17073-green-13-puzzle-original-version