To solve Shikaku, list the rectangles each number could be, and draw the ones that fit only one way. Every rectangle you draw takes squares away from the numbers around it, so more of them fit only one way. When that stops, look for squares every option of a number covers, and squares only one number can reach. Three techniques cover every puzzle in the game.
New to Shikaku? Read the Shikaku rules first. This page assumes you know the three: one number in each rectangle, the number is its area, and the rectangles cover the grid.
1. Only one fit
For each number, think of the rectangles it could be: its area must match, it must hold the number’s square, and it can’t hold another number or overlap a rectangle already drawn. A number with only one rectangle that fits gets that rectangle. Numbers like 5 and 7, which can only be straight lines, are often the first to go.
2. Overlap
When a number still has several rectangles, look at the squares they all share. Squares that every rectangle of a number covers are certainly that number’s, so no other number’s rectangle can use them.
3. Only one number can reach
Turn it round: every square belongs to some rectangle. A square that only one number’s rectangles can reach must be in that number’s rectangle, so its rectangles that miss the square are out.
When all three run out, what-if (try a rectangle, and see whether some number runs out of room) would come next, but none of the game’s levels needs it.
How often each technique is needed
We solved every one of the game’s 150 levels by following the hints, which always use the simplest technique that works. This is how many times each technique was used, on average, per level:
| Technique | Easy 7×7 | Medium 10×10 | Hard 12×12 |
|---|---|---|---|
| Only one fit | 12.3 | 19.9 | 26.8 |
| Overlap | 1.4 | 5.3 | 11.0 |
| Only one number can reach | 0 | 0.9 | 5.7 |
Only one fit places every rectangle in the end; the other two clear the way. Overlap is needed on 31 of the 50 Easy levels, 48 Medium and every Hard one; only one number can reach on 9 Medium levels and every Hard one.
A 10×10, solved in stages
This is Medium level 35 from the game.
Stage 1: what fits one way
Seven numbers have only one rectangle that fits, one after another as each rectangle drawn takes squares from the next.
Stage 2: overlap
Nothing else fits only one way, so look for overlap. The 8 in row 2, column 5 has four rectangles left, and every one covers the two squares below it, in rows 3 and 4. That rules out 4 rectangles of the 6 in row 3, column 3 and the 8 in row 5, column 6. Straight after, the 8 in row 5, column 6 is sure of the three squares below it, which rules out rectangles for three more numbers.
From there, it’s overlap and only one fit to the end. In all, the level takes 31 steps: 24 where a number fits only one way and 7 from overlap.
When you get stuck
- List each number’s rectangles, counting the ones that clear every other number and every rectangle already drawn.
- Draw any that fit only one way, then look again: each one changes its neighbours.
- Look for squares every option of a number covers.
- Look for squares only one number can reach.
- Don’t guess. Every puzzle here can be finished by logic.