The fastest way to get better at Shikaku is to start with the numbers that have the fewest shapes, work in from the edges, and look around every rectangle you draw. We measured these tips on all 150 of the game’s levels, and the numbers below come from those tests.
These build on how to solve Shikaku. If you haven’t played before, start with the rules.
Solving tips
1. Start with numbers like 5 and 7
A 5 or a 7 can only be a straight line, one square wide. So can 2, 3, 11 and 13. They have fewer rectangles to choose from: 2.4 at the start, on average, on the Easy levels, against 3.9 for numbers like 4, 6 and 8 (3.1 against 5.0 on Medium, 3.3 against 6.5 on Hard).
2. Work in from the edges
The edge of the grid cuts a number’s options down. Most rectangles touch it: 74% on the Easy levels, 58% on Medium and 53% on Hard.
3. Let each rectangle squeeze its neighbours
Every rectangle you draw takes squares away from the numbers around it, and often leaves one of them only one shape. Most of the solve is exactly that: 90% of the steps on Easy are a number that fits only one way, 76% on Medium and 62% on Hard.
4. Look for overlap when nothing fits one way
When every number still has a choice, find a number whose rectangles all share some squares. Those squares are its, and no other number can use them. On Hard, that’s 11 steps per level on average.
5. Ask which number can reach a square
Every square belongs to some rectangle. A square that only one number can still reach has to be in that number’s rectangle. It’s needed on every Hard level, 5.7 times each on average.
6. Draw only what you’re sure of
A rectangle in the wrong place with the right area breaks no rule, so nothing turns red. You only find out when another number runs out of room, which can be a long way on (see common mistakes).
Tips for playing on PeerPuzzles
7. Drag to draw, tap to remove
Drag from one corner of a rectangle to the other. While you drag, a label shows its size, like 3×2 = 6, so you can match it to the number. Drawing over old rectangles replaces them; a tap removes one. Ctrl/Cmd + Z undoes a move, and H asks for a hint.
8. Let the outlines and Stuck? help
A rectangle with the wrong area, two numbers or none is outlined in red. If you’re stuck, Stuck? highlights the number to look at and names the technique, without drawing the rectangle for you. If one of your rectangles is wrong, it outlines that one first.