> <i>Maybe now I can shift my irritation from the lamp itself to whoever designed it to possess such a property.</i><p>There's no "design" involved in the choice of pieces: there are seven different ways to connect four squares in an orthogonal grid, "tetrominoes", assuming you allow for pieces to be rotated but not reflected. Tetris uses all seven, and so does the lamp. (Although the lamp's design apparently allows pieces to be reflected, i.e. rotated outside of the grid, so the S and Z pieces can be considered the same, as can L and J.)