The invention comprises a plurality of rectangular prism and/or cubic blocks. The sidewalls of the blocks comprise various combinations of grooves and/or pegs. Each groove extends along the respective sidewall within which it is disposed, from a corner wherein the top wall and the respective sidewall intersect to a corner wherein the bottom wall and the respective sidewall intersect. Each peg is configured to be slidably received into a groove disposed on another block within the plurality of blocks.