"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. a wooden cube, sphere, barrel, or teddy bear may all have similar Cartesian internal construction and so should all be classed as Interlocking-Cartesian). In cases where it seems possible to place a puzzle in more than one category, it must be classified in whichever is the most significant category. A few puzzles may have to be cross-referenced if it is absolutely necessary; however in most puzzles, which include two different classes of problem, one class will usually be dominant by virtue of the fact that in solving it, the secondary problem has also been solved.
A good example of multiple-class puzzles is the 'Mazy Ball Game' made in Taiwan in the 1990s - It is based on a 3x3 sliding block puzzle under a clear plastic top - The pieces have L-shaped groves and a ball must be rolled up a ramp in the lower right onto one of the blocks - the ball must be moved from block to block and the blocks themselves slid around so that the ball can exit at the top left. Thus the puzzle requires Dexterity, Sequential movement and Routefinding. It would be classed as Routefinding because, if the route has been found, then the dexterity and sequence must have also been achieved.
A puzzle will be referred to as 2D if its third dimension is irrelevant (e.g. thickness of paper or plywood or an operation involving a third dimension such as folding). Most standard jigsaws are 2D; however jigsaws with sloping cuts in fact have a relevant third dimension, so they must be classed as 3D.
It will be noted that the definition of 'A Puzzle' excludes the infants 'posting box' which whilst perhaps puzzling the infant was contrived only to educate and amuse; it also excludes the archer attempting to get a bulls‑eye, the exercise of whose ingenuity is entirely incidental to the original warlike intent of the sport. Also excluded are puzzles that only require paper and pencil (e.g. crossword puzzles), unless they are on or part of some physical object. It is understood that specialist collectors will further subdivide the Sub‑Classes to suit their own specialised needs. For example, Tanglement Rigid & Tanglement Semi-Rigid is awaiting a thorough study of the topology of wire puzzles.
The full abbreviations consist of 3 characters, hyphen, plus up to 4 characters, such as 'INT‑CART'. These are the standard abbreviations for the classes that have been chosen for relative ease of memory and conformity with most computer databases."