Vanishing puzzle

A vanishing puzzle is a mechanical optical illusion comprising multiple pieces which can be rearranged to show different versions of a picture depicting several objects, the number of which depending on the arrangement of the pieces.

[3] Cutting the rectangular card into four oblongs allowed the pieces to be rearranged to show either 8, 9 or 10 eggs.

[4] Chess player and recreational mathematician Sam Loyd patented rotary vanishing puzzles in 1896 and published versions named Get Off the Earth, Teddy and the Lion and The Disappearing Bicyclist (pictured).

Each had a circular card connected to a cardboard backdrop with a pin, letting it freely rotate.

[9] The missing square puzzle is an optical illusion used in mathematics classes to help students reason about geometrical figures; or rather to teach them not to reason using figures, but to use only textual descriptions and the axioms of geometry.

Interactive SVG of The Disappearing Bicyclist – in the SVG file, move the pointer to rotate the disc
Interactive SVG of The Magic Egg Puzzle – in the SVG file, move the pointer to cycle its upper half
Simplified rotary (left column) and sliding (right column) vanishing puzzles showing 2, 3 or 4 bars depending on the position of the moving part (yellow)