Ten Billion Barrel Puzzle

The Ten Billion Barrel, also known as the Nintendo tumbler puzzle, is a mathematical puzzle in the style of Rubik's Cube.

It consists of a "cylinder" divided into six levels, together with a black plastic "frame". The frame consists of upper and lower discs that are joined together through the middle of the cylinder.

The top and bottom levels of the cylinder form a single piece, but between them are two rotatable pieces each two levels high. Each of the four central levels is divided into five chambers each containing a coloured ball. The top and bottom levels have only three chambers, containing either three balls or three parts of the frame depending on the relative position of frame and cylinder.

The balls in three of the five resulting columns of chambers can be moved up or down one level by raising or lowering the frame relative to the transparent cylinder.

The aim is to place four balls of the same colour in each of the five columns, with the three black balls filling up the top of the longer columns.

[Source: Wikipedia & Jaap's Puzzle Page)