The rainbow ball cube is a puzzle with the very simple objective of matching the colour of different balls with a correspondingly coloured ring. The cube is designed with one opening at one of the sides, through which all the balls need to be permuted in order to match each one with the same-coloured ring. There are also a couple of variants which have different designs and objectives, but work on the same principle.
Ball cubes are extremely useful for improving spatial skills, thinking ability, as well as colour recognition. It is extremely fun and engrossing especially for kids, as they can enjoy figuring out different ways of getting each ball to the right coloured ring. It also comes in a mini size that has a lower number of rings as compared to the original.