How to play Shikaku

Shikaku is a grid puzzle about finding a home for every number. Divide the board into rectangles until every square belongs to one.

Three rules. One filled grid.

1. One number in each rectangle. A rectangle cannot contain two clues, or no clue at all.
2. The number is its area. A clue of 6 needs six squares. That could be 2 × 3, 3 × 2, 1 × 6, or 6 × 1, if the board has room.
3. Cover every square exactly once. Rectangles cannot overlap, and there must be no empty squares when you finish.

Make your first rectangle

Choose a number near an edge. List the rectangle shapes with that area, then see which ones stay inside the board without taking in another number. A 5 can only form a single row or column of five squares; a 6 has more options.

Look at empty corners and narrow gaps, too. A rectangle may fit its own clue but leave a square that no other clue can reach. You win by fitting the whole board together.

Mouse, touch, or keyboard

• Drag: press in one corner square and release in the opposite corner square.
• Tap or click twice: select the first corner, then the opposite one. The whole rectangle between them is included.
• Keyboard: tab into the grid, move with the arrow keys, and press Enter or Space to choose each corner. Press Escape to cancel.
• Change your mind: Undo reverses your last change. Erase lets you tap a filled rectangle to remove it. In the grid, Delete removes the rectangle under your focus. Clear empties the board and can be undone.

When you need a little help

A hint outlines one rectangle that can lead to a complete solution. You can place it or keep thinking. If an existing rectangle prevents a complete solution, the hint first shows you which one to remove. A move that matches one clue is not always the right move for the whole puzzle.

Daily or at your own pace

Each board size has its own daily puzzle, changing at 00:00 UTC. Practice lets you explore 18 boards in each size: 5 × 5, 6 × 6, and 8 × 8. Daily boards rotate through the same original collection, repeating every 18 days per size. Your saved daily stays open across midnight and reopening; Play today asks before opening the new date. Earlier dated records are kept.

Continue practice returns to your saved practice puzzle. Each board size remembers its own practice position. Next puzzle asks before leaving an unfinished attempt.

Each puzzle has exactly one complete solution.

Your current boards and preferences are saved in this browser when storage is available. The timer pauses when the page is hidden. Progress does not sync between devices, and clearing browser data removes it.