A clean Hitori finish in the browser takes five shades and lands at 950 points from a starting score of 1,000, because each shade counts as a move and the score formula is max(0, 1,000 minus 10 times the move count). The actual work is rarely about placing those five blacks and is more about spotting exactly which five cells of the five by five grid to shade while honouring three constraints at once. Every visible number must remain unique in its row and column once the blacks are removed, no two black cells may share an edge along the orthogonal grid lines, and all white cells must form a single connected region through up, down, left, and right neighbours. The fixed Hitori Puzzle board opens with deliberate duplicate pairs, so a sensible rhythm is to spend the first pass on duplication analysis, the second pass on adjacency and connectivity, and the final pass on unhading any black that breaks the network. Treat the constraints as a single checklist rather than a sequence of three separate puzzles and the run becomes much more predictable.
The Three Constraints to Keep in Mind
Hitori is deceptively compact because the rules are short but the constraints interact. The elimination rule alone — no repeated number in any visible row or column — is a familiar puzzle pattern, and on its own it would not need much more than pencil-and-paper duplicate marking. The added geometry is what turns Hitori into a deductive game: black cells cannot touch along an edge (diagonals are fine), and the remaining white squares must all connect through up, down, left, and right neighbours. The three constraints follow Nikoli's official Hitori explanation and the independent Singles documentation in Simon Tatham's Portable Puzzle Collection, so the rule set is well documented and not invented by any single host.
Because the three constraints must all hold simultaneously, a partial reading is dangerous. You can satisfy the duplicate rule by shading every duplicate, then immediately break adjacency by shading two stacked numbers in the same column. You can satisfy adjacency and uniqueness while accidentally walling off a single white cell that becomes an orphan. Treat the constraints as a checklist, not a sequence: every move must keep all three promises, not just one of them.
How to Use Hitori Puzzle on Lizely
The tool itself is a single keyboard-driven board with a fixed five by five layout. The current cell has a visible site-theme outline that shows which cell is selected. Validation runs after every shade and a contradiction banner appears whenever one of the three constraints fails.
- Move through the grid with the arrow keys. Each press moves the selection one cell up, down, left, or right, and the cursor stays inside the five by five bounds.
- Press Space to shade or unshade the selected cell. Shading turns the cell black and starts contributing to the duplicate and adjacency checks right away.
- Press Enter to add or remove a white-circle note on the selected cell. A note means you have decided this cell stays white and never counts against the rules.
- Remove every visible row and column duplicate to finish; correct contradictions or select Restart to begin again.
- Read the contradiction banner whenever it appears. It tells you the current arrangement has failed — usually a pair of edge-adjacent blacks or a split white region.
- Unshade a problematic cell with Space, or select Restart to clear every shade, note, and counter and start over from a fresh score.
- Stop when validation shows zero duplicates, no adjacent blacks, and one connected white area. The score freezes at 950 for a five-shade clean run.
Mouse and touch users have an equivalent path. A click shades or unshades the cell under the pointer, while a context-menu action toggles the white-circle note. After the puzzle is solved, input freezes until Restart so the completed state stays visible rather than drifting away on a stray keystroke.
Practical Tips That Hold Up on a Five by Five Grid
Most of the time spent on a five by five board is not on placement but on reading the grid correctly. The first tip is to scan every row and column for repeated numbers and treat those as the only candidates for the first pass. The second tip is to look at the corners: a corner cell often has only two neighbours, so shading it carries a low adjacency cost and a high connectivity cost. The third tip is to search for A-B-A patterns in a row or column, because the middle B can usually be marked as a note and the two As become shading candidates. This is one of the most reliable starting patterns in Hitori, and the technique carries over directly to the fixed five by five layout.
A second batch of habits matters once the first few shades are down. Use notes aggressively on cells you have proved must stay white, because the visual record stops you from re-arguing the same cell every pass. Do not place a note on a cell you might want to shade later — shading automatically removes the note, but only because the cell has now changed state. After each shade, glance at the row and column counters again, because a single new black often resolves a duplicate you had not yet noticed. The puzzle freezes only after completion, so mid-game validation is your friend.
A short table of where constraints most often break helps when you are stuck:
| Constraint | Common slip | How to spot it |
|---|---|---|
| Row and column uniqueness | Shading only one of a duplicate pair | The same number still appears twice in a visible row or column |
| No edge-adjacent blacks | Shading two stacked or sideways neighbours | A vertical or horizontal pair of black cells sits next to each other |
| One connected white area | Walling a single white cell off with blacks on all sides | An isolated 1x1 white pocket remains inside a ring of black |
If you want a deeper look at how the three constraints interact before you start shading, the Lizely guide on Hitori rules and the three constraints walks through the same logic in more detail. For the diagonal question specifically — which catches many first-time players — the black cells touching diagonally in Hitori article gives the rule in one line.
When the Contradiction Warning Fires
The contradiction message is a current-state warning, not a permanent game over. It means the present arrangement has failed one of the three checks: a duplicate count above one, an edge-adjacent pair of blacks, or a white region that the breadth-first traversal cannot reach from a starting white cell. The browser recounts values after every shade, rechecks each black's right and lower neighbours for forbidden adjacency, and reruns the white-component traversal — so the message tells you exactly what the board looks like at the moment you triggered validation.
The recovery is usually to unshade a single cell rather than restart the whole board. Press Space on the most recent black and look for the row, column, or white pocket that changes status. If the board is now too tangled to read, Restart clears every shade, note, move count, and contradiction at once and resets the score. Unshading with Space is the direct way to backtrack, and a quick Restart is faster than untangling a bad branch by hand.
Reading the Score
The score is straightforward: it starts at 1,000 and drops by ten for every move you make, with a floor of zero. A move is any action that changes the board — every shade and every note. A clean five-shade solution with no notes therefore scores 1,000 minus 10 times 5 = 950 points. Notes cost the same ten points each but they do not affect validation, so they are most useful on cells you have proved white and want to mark visually. If you want a stronger score on a tougher board, save notes for final confirmation and shade only when you have reasoned out the cell.
The browser may store a best score in localStorage so the next visit knows your previous result, but nothing is uploaded and the gameplay itself is entirely local. If you ever need to hide the puzzle — for example, during a meeting — pressing Escape twice within 400 milliseconds shows a shared simulated operations spreadsheet, and a second double-press restores the unchanged board. This boss cover is visual only; it does not pause validation or move counting.
Other Logic Breaks Worth Trying
If Hitori becomes a comfortable routine, the same short deduction break style carries over to a few other deterministic logic boards. Hashi Bridges asks you to connect numbered islands with non-crossing bridges, which exercises the same breadth-first reasoning on a different grid. Nonogram is a compact picture-logic puzzle where every row and column clue has to be satisfied simultaneously, which mirrors Hitori's "three constraints at once" feeling. For pure keyboard play with no cognitive-test framing, Maze Game is a short arrow-key run through a fixed corridor map. Use any of these as a five-minute break rather than as a measure of attention or skill.