Invented in 1966 by Patrick Rylands, over a million sets of this ingenious toy were sold before they went out of production.  Recently reintroduced with the help of the original designer and produced with the original colors by the original English factory.  In the permanent collection of the V&A Museum, London.  An example of how the best toys are the simplest.  Enjoy the play of color through the clear polystyrene.  48 squares in 5 colors.