Shikaku
Play Shikaku free online: divide a grid into rectangles where each rectangle's area matches its number. A spatial math puzzle with Retro Coins.
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How it works
Play, earn points and Retro Coins: the shared currency across every RetroPlayNow game. Unlock badges and climb the leaderboard! Your progress is saved automatically on this device.
Shikaku, also known as Rectangles, is a puzzle of geometric division. A grid contains scattered numbers. Your task is to divide the entire grid into rectangles (and squares) such that each rectangle contains exactly one number, and the area of that rectangle (its width times height) equals that number.
The puzzle begins with simple deductions. A 4 in a corner can only form a 1x4 or 2x2 or 4x1 rectangle. A prime number like 7 can only form a 1x7 or 7x1 rectangle — it cannot be a square. A 1 is always a 1x1 square by itself.
As the grid fills, the spatial reasoning deepens. Each rectangle you place constrains its neighbors. A 6 might be 2x3 or 3x2 or 1x6 — but only one of those shapes will fit without overlapping other rectangles or leaving isolated cells that cannot form valid rectangles.
Our RetroPlayNow version offers puzzles at multiple sizes, a drag-to-draw rectangle interface, real-time area feedback, and error highlighting for overlaps. Every completed division earns Retro Coins based on puzzle size and solving time.
How to play Shikaku
- Draw rectangles around numbers. Divide the grid into rectangles. Each rectangle must contain exactly one number.
- Match area to number. The area of each rectangle (width × height) must equal the number it contains.
- Cover the entire grid. Every cell must belong to exactly one rectangle. No overlaps, no gaps.
- Use prime numbers first. Prime numbers can only form 1×N rectangles. This constrains their placement and helps you start the puzzle.
- Earn Retro Coins. Complete puzzles to score points based on size and solving time. Faster solutions earn more Retro Coins.
