Classification of Mechanical Puzzles

"A puzzle should be classified by the problem that its designer intended the solver to encounter whilst attempting to solve it. In the case of a 3D interlocking assembly in the form of a cage with a ball in the centre: the fact that the instructions request the would-be solver to 'remove the ball' does not change the 3D assembly into an opening puzzle. The disassembly and/or reassembly of the cage remains the primary function of the puzzle. An interlocking puzzle should be classified according to its interior construction, rather than its outward appearance (e.g.