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Shikaku (also known as Divide by Box) is a captivating logic puzzle invented by the Japanese puzzle company Nikoli. The objective is to divide a rectangular grid into non-overlapping rectangles and squares.
Each rectangle must contain exactly one number, and the area of that rectangle must exactly equal the number inside it. Unlike Sudoku, Shikaku tests your spatial reasoning and area calculation skills, making it a highly rewarding mental workout.
You are presented with a grid containing scattered numbers. Your goal is to draw borders to form rectangles or squares around these numbers.
A valid rectangle must contain exactly one number. The number dictates the area (number of cells) of that rectangle. For example, a '4' can be a 2x2 square or a 1x4 line. The puzzle is solved when the entire grid is covered with valid rectangles and no empty spaces remain.
Begin by finding prime numbers or large numbers near the edges. A '7' can only be a 1x7 or 7x1 line, which often fits in only one possible direction on the board.
Look for bottleneck cells—empty squares that can only be reached by one specific number's rectangle. As you box off numbers, the remaining space for unsolved numbers becomes smaller, leading to a satisfying chain reaction.
Shikaku is excellent for improving spatial awareness and practicing multiplication and area calculation. It forces your brain to visualize geometric shapes before committing to a move.
Regularly solving Shikaku puzzles helps enhance your short-term memory and logical deduction skills without the math-heavy stress of other numerical puzzles.
Only basic multiplication! You need to know the factors of the numbers on the grid (e.g., 6 can be 2x3 or 1x6) to determine the possible shapes of the rectangles.
Yes, every properly designed Shikaku puzzle has exactly one unique solution that can be reached purely through logical deduction without guessing.
Shikaku was invented by Nikoli, the famous Japanese puzzle publisher that also popularized Sudoku.