Cell Blocks (also known as Shikaku) is a clean, satisfying logic puzzle where your goal is to divide a grid into rectangles. Each rectangle must contain exactly one numbered clue, and its area must match that number. No arithmetic, no guessing — just pure spatial reasoning.
The Objective
Partition every cell of the grid into non-overlapping rectangles (including squares). Each rectangle must contain exactly one clue number, and the total number of cells in that rectangle must equal the clue.
The Tools You Have
Choose a grid size — 5×5, 6×6, 7×7, 8×8, or 14×14 — from the dropdown in the header. The New Game button generates a fresh puzzle at the current size. On the board, numbered clues are printed in certain cells; these are fixed and cannot be moved.
How to Draw Rectangles
- Click and drag across cells to draw a rectangle. Release the mouse to confirm it.
- The rectangle snaps to the bounding box of your drag, so you always get a clean rectangular shape.
- A blue preview shows the rectangle you are about to place while you drag.
- If a new rectangle overlaps any existing ones, the old ones are removed and replaced by the new one.
- Click on an existing block (without dragging) to remove it.
The Rules to Follow
- Every cell must be covered: no gaps are allowed when the puzzle is complete.
- No overlaps: rectangles may not share cells.
- One clue per rectangle: each rectangle must contain exactly one numbered clue.
- Area equals clue: if a clue reads
6, its rectangle must cover exactly 6 cells (e.g., 1×6, 2×3, 3×2, or 6×1). - Rectangles only: L-shapes, T-shapes, or other irregular regions are not allowed.
Reading the Feedback
- Coloured fill: each confirmed rectangle gets a distinct background colour so you can tell the regions apart at a glance.
- Red fill: a rectangle whose area does not match the clue inside it, or that contains more than one clue, is highlighted in red.
- Congrats overlay: when every cell is covered and every rectangle is valid the puzzle declares you solved!
Simple Strategy
Start with clues whose value equals the number of cells remaining in a row or column — those rectangles have only one possible orientation. Large clues (like 12 or 14) also heavily constrain placement since few rectangle shapes fit the remaining space. Small clues near corners or edges are often uniquely determined by the available room.
Example of Play
In a 6×6 grid, a clue of 6 along the top row with walls on both sides can only be a 1×6 horizontal strip covering the entire row. A clue of 4 in the corner can only be 1×4 (extending right or down) or 2×2 — the neighbouring clues and borders tell you which. Lock in the forced rectangles first; the rest of the grid follows.
Tips for Beginners
- Corners and edges first: cells in a corner have at most two expansion directions, making the rectangle nearly forced.
- Big numbers, big rectangles: a clue of 8 in a 6-wide grid must span at least two rows — that alone eliminates many shapes.
- Work by elimination: if only one rectangle shape fits a clue without covering another clue, that shape is correct.
- Remove and retry: click a block to erase it and try a different shape — there is no penalty for guessing.
- Larger grids, same logic: 14×14 introduces more clues and more room, but the partitioning rules are identical — take it one region at a time.