What Is Hitori? Rules and Beginner Strategy

What is Hitori?

What is Hitori at its core? It is a number shading puzzle that works by elimination rather than placement. You start with a square grid already filled with numbers, and your task is to shade out certain cells so that no number appears more than once in any row or column. Hitori adds two guardrails: shaded cells may never touch each other side by side, and all the unshaded cells must remain connected in one single group. It is the rare logic puzzle where you remove information to reveal the answer.

The three rules

Everything about what is Hitori asks of you fits into three clear rules.

• After shading, no number repeats within any single row or any single column.
• Two shaded cells may not be horizontally or vertically adjacent.
• All unshaded cells must form one connected area, reachable from each other without crossing a shaded cell.
• Numbers you keep unshaded stay exactly as printed.

Beginner strategy

The clearest path into what is Hitori runs through pairs and triples of matching numbers.

1. When the same number appears three times in a line, the middle one usually must stay, because shading both ends would strand it, so the outer two get shaded.
2. For a pair of identical numbers with a copy elsewhere, deductions about which can survive quickly follow.
3. Once you shade a cell, mark its four neighbors as definitely unshaded, since shaded cells cannot touch.
4. Any number that would be left alone and unique can be confirmed as unshaded.
5. Constantly check that your shading has not cut the grid into disconnected pieces.

Keeping the grid connected

The connection rule is the soul of Hitori and the source of many clever deductions. If shading a cell would isolate a corner or split the board into two islands of unshaded cells, that cell must stay unshaded instead. Experienced solvers use this constantly. Sometimes you cannot prove a cell directly from the number rule, but you can prove it must stay light because shading it would break connectivity. That single insight resolves many otherwise stubborn spots.

Avoiding touching shaded cells

The no touching rule pairs neatly with connectivity to create chains of certainty. Whenever a cell is shaded, its neighbors are forced unshaded, and those forced light cells often trigger new number based deductions. Working these two rules together, rather than one at a time, is what makes Hitori flow. As always in a well made puzzle, every step is provable, so there is never a need to guess.

If you like Hitori, try shape Sudoku

Hitori and Sudoku are cousins in spirit. Both forbid repeats in rows and columns, and both reward calm elimination over luck. If that style of thinking suits you, Shapedoku offers a warm, number free version of the idea. It keeps the classic Sudoku rules across every row, column, and three by three box but swaps the digits one through nine for nine glowing shapes, distinct by both shape and color so colorblind players can enjoy them too. Try the free daily challenge at app.shapedoku.com, or study the built in solver on shapedoku.com.