We study the computational complexity of packing puzzles of identical polyominoes. Packing dominoes (i.e., 1 × 2 rectangles) into grid polygons can be solved in polynomial time by reducing to a bipartite matching problem. On the other hand, packing 2 × 2 squares is known to be NP-complete. In this paper, we fill the gap between dominoes and 2 × 2 squares, that is, we consider the packing puzzle...
