The fastest way to get better at Hitori is to let the puzzle lead you: sweep for sandwiches first, then follow the chain from every square you settle, and watch the edges for squares you can’t shade. 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 Hitori. If you haven’t played before, start with the rules.
Solving tips
1. Sweep for sandwiches first
A number between two of the same stays unshaded. Every one of the game’s levels has at least one on the empty grid, and they come early: 84% of the sandwiches in an Easy solve are found before any other kind of move, 81% on Medium and 63% on Hard. Go along every row and down every column and circle them all before you think about anything else.
2. Then look for pairs with a third copy
Two of the same number side by side, with a third copy elsewhere in the line: one of the pair stays, so the third is shaded. They’re rarer than sandwiches, but most levels have one somewhere.
3. Keep the chain going
Every square you shade circles its neighbours, and every number you circle shades its twins. On the game’s levels, the next move starts from a square the last move settled 57 to 58% of the time, at every size. Follow the chain before searching anywhere else.
4. Circle as you go
Circle every square you know stays unshaded. A circled number tells you its twins must be shaded, and the circles show you which squares still need joining up. Without them, you’re keeping all of that in your head.
5. Watch the edges for cut-offs
When the chain stops, look for a square whose shading would wall something in or cut the grid in two: it stays unshaded. These are more common near the edge: 70% of the cut-off squares on Easy are on the edge (which is 64% of the grid), 62% on Medium (49%) and 52% on Hard (40%). A corner square with a shaded neighbour is the classic case.
6. On Hard, expect a what-if
Every Hard level needs at least one what-if, about 2 per puzzle on average. When nothing else is left, pick a square next to a shaded one, suppose it’s shaded, and follow the chain a few moves. If something gets walled in or repeats, it stays unshaded.
Tips for playing on PeerPuzzles
7. Tap to cycle, right-click to go back
A tap cycles a square from plain to shaded to circled and back to plain. On a computer, right-click cycles the other way, so circling is one click.
8. Let the red marks and Stuck? help
A repeated circled number turns red, touching shaded squares get a red outline, and a finished grid that’s split gets a red frame. Undo (or Ctrl/Cmd + Z) takes back a move. And if you’re stuck, Stuck? (or H) highlights the squares to look at and names the technique, without giving the answer away. If one of your squares is wrong, it rings that square first.