Signal : Grid tiling or covering problem. Tiles are small shapes (dominoes, tetrominoes). Signal : One dimension is small (≤ ). The other can be large (up to with matrix exp). Signal : Local constraints.
Each placement depends on nearby cells, not global properties. Not applicable: if both dimensions are large, if tiles are irregular, or if constraints are global (.., total count). Recognizing this pattern early saves time during problem-solving.