A mathematical puzzle used to assess problem-solving and planning skills. Conventionally, it involves three pegs and a set of disks stacked in increasing order of size on the first peg. The goal is to move disks one by one to the last peg, with the constraints that larger disks cannot be placed atop smaller disks, and this maneuver must be done in the least number of steps possible. Number of disks and pegs can be changed to adjust difficulty.