Patent ID: 7997902
Filing Date: 2011-08-16
Classification: G09B

Abstract:
1. Apparatus comprising a plurality of pieces and a base, board, screen or tray carrying a regular array of indicia, wherein the pieces are dimensioned and arranged, and the indicia are arrayed, to allow a plurality of said pieces to be juxtaposed adjacent to the indicia, covering a plurality of the indicia, such that each piece covers a single one or an integral number greater than one of the indicia, wherein the pieces each comprise a transparent or translucent material, each of the indicia so covered by a piece is visible through the transparent or translucent material in that piece, said transparent or translucent material has a higher refractive index than air, and each piece is shaped such that, as a result of internal reflections within the transparent or translucent material in said piece, it is substantially impossible for a covered one or group of the indicia to be viewed through a combination of the covering piece and another adjacent piece.