Most puzzle cubes are solved by making each face one solid colour. The Sub-Cube is different: each face still has a colour, but it's not one continuous piece. Each of the moving pieces of the cube has the colours of the two or three faces it touches, and in its solved state, each square on a face of the Sub-Cube contains some of the central colour for that face. Instead of the three colours around each corner of the cube (or the two where faces meet) being arranged so there's one on each face, they're symmetrical. The corner and edge pieces can be rotated and flipped, without changing the appearance of the cube. The symmetry group of the Sub-Cube - the set of possible states it can be in - is a subgroup of the symmetry group of a regular puzzle cube. Even though it's smaller, it still has 9,656,672,256,000 different combinations! Designed by Katie Steckles for Maths Gear, based on an idea by Christian Lawson-Perfect. Price = 1297 pence (the 211th prime number) = £12.97
