Two of our best sellers are the place to start.
Safecracker 50 is Dave Janelle's design: five rotating rings and sixteen columns, 1,048,576 possible positions, and exactly one where every column adds up to 50.
Calibron 12 is our faithful reproduction of the 1933 puzzle by Theodore Edison, Thomas Edison's youngest son, and the job is to fit twelve wooden blocks into a single rectangle. For the hardest tier,
Martin's Menace is Stewart Coffin's design number 217, made with his permission, and it belongs to our
Impossible Puzzle Series, which we rate 11 out of 10. More of Coffin's designs are in our
Stewart Coffin puzzles.