Abstract: An improvement is disclosed in a puzzle of the type including a rectangular base piece, a raised rectangular frame surrounding the sides of the base piece and defining therewith a recessed platform; and a plurality of rectangular flattened pieces which are positionable on said platform within said frame, and of dimensions and number when so positioned in mutual lateral contact as to provide a single rectangular void space among the pieces; the flattened pieces being slidable on the plane of the platform subject to lateral restraint by one another; and the object of the puzzle being to proceed from a designated starting configuration of the flattened pieces, and interchange the respective initial positions of designated of the flattened pieces by successive sliding movements of pieces into and out of the said void space.

Abstract: An improvement is disclosed in a puzzle of the type including a rectangular base piece, a raised rectangular frame surrounding the sides of the base piece and defining therewith a recessed platform; and a plurality of rectangular flattened pieces which are positionable on said platform within said frame, and of dimensions and number when so positioned in mutual lateral contact as to provide a single rectangular void space among the pieces; the flattened pieces being slidable on the plane of the platform subject to lateral restraint by one another; and the object of the puzzle being to proceed from a designated starting configuration of the flattened pieces, and interchange the respective initial positions of designated of the flattened pieces by successive sliding movements of pieces into and out of the said void space.