The next useful move in a Shikaku puzzle is not always the largest rectangle. Often it is the clue with the fewest places left to go. A reliable solving routine separates what is possible from what is forced.
If you are new to the puzzle, begin with the Shikaku rules and worked example. The techniques below assume you already know what makes a region legal.
List shapes before choosing positions
For a clue of 12, possible dimensions include 1 × 12, 2 × 6 and 3 × 4, plus their rotations. On a board that is only five cells wide and five tall, the first two options cannot fit. A 3 × 4 or 4 × 3 rectangle may still work.
This does not identify its exact position. A clue may sit at a corner, along an edge or inside a rectangle. After narrowing the dimensions, slide each possible shape mentally around the clue and eliminate placements that cross the boundary, another clue or an established region.
Look for clues close to boundaries
An edge removes placements on one side. A corner removes them on two sides. That makes edge clues worth checking, but it does not make every edge clue immediately solvable.
Imagine a clue of 5 on a board only four cells high. The vertical five-cell strip cannot fit, so any solution must use a horizontal strip. You still have to decide how far that strip extends left and right. Nearby numbers and the board edge provide the next restrictions.
Ask who can cover an awkward cell
Instead of studying one number, choose an empty cell near a corner or in a narrow gap. Identify every clue that could legally cover it. If only one clue has a valid rectangle reaching that cell, that clue must take responsibility for it.
Now compare all remaining placements of that clue. Any cell shared by every possible placement must belong to that region, even if the rectangle’s complete boundary is not yet known. You can use that information mentally without committing a premature rectangle in Sukto.
Check the space a move leaves behind
A locally legal rectangle can still make the rest of a board impossible. Before committing, look at the empty space around it. Have you trapped an isolated cell that no remaining clue can reach? Have you cut a narrow corridor that cannot form a legal rectangle?
Area provides another check. If completed regions fully separate an unfinished area, the clues inside that area must account for exactly its cells. A mismatch shows that at least one assumed boundary needs to change. This is a consistency check, not permission to ignore the shapes of those regions.
Use a repeatable scan
Try this order when a board feels crowded:
- Eliminate dimensions that cannot fit the board.
- Examine corners and constrained clues.
- Find cells that only one region can reach.
- Check the consequences of a proposed rectangle.
- Repeat after each new deduction.
If you become stuck, revisit the most uncertain placement instead of drawing faster. In Sukto, tap an occupied cell to remove its region and test your revised reasoning.
Sukto accepts any complete partition that satisfies its rules. Its generated boards are guaranteed to have a solution, but the app does not promise that every board has exactly one. Read our guide to common mistakes for more ways to distinguish a valid rectangle from a completed solution.
