Based on a puzzle originally by Donald Knuth and George Miller, Cubigami 7 challenges you to find ways to fold this arrangement of 18 hinged plastic squares into seven of the eight possible arrangements of four connected cubes, or tetracubes.
Incredibly, they can all be folded from the same net - and when opened out flat, the whole thing fits into a six-by-six square. Warning - some are more difficult to make than others!
Price = 997 pence (the 168th prime number) = £9.97