Nurikabe vs Hitori: Rules, Differences, and Which to Try
Nurikabe and Hitori are both Nikoli grid puzzles built around shading cells black — but what you shade, why you shade it, and how you figure out your next move are fundamentally different in each. If you have seen both names come up and still could not explain the difference on the spot, this comparison lays it out side by side: rules, starting conditions, the feel of solving each one, and a clear way to pick the one that suits you.
Quick answer: Nurikabe is a territory puzzle — a mostly blank grid where numbered cells are clues for island sizes, and you paint the sea around them. Hitori is an elimination puzzle — a completely filled grid where you shade duplicate numbers away until each row and column is clean. Same origin (Nikoli, Japan), opposite starting conditions, different logic styles.
What Is Nurikabe?
Nurikabe is a logic puzzle first published by Japanese puzzle company Nikoli in 1991. According to the Wikipedia article on Nurikabe and Nikoli’s official Nurikabe page, the puzzle takes its name from a creature in Japanese folklore — a supernatural spirit said to block travelers’ paths, which fits the visual of the black “sea” walls that close in around and separate every island.
The starting grid is mostly blank. A handful of cells contain numbers; every other cell is empty. Your job is to decide which blank cells become white (part of an island) and which become black (part of the sea). The four rules that govern those decisions:
Rule 1 — Islands match their clue. Each numbered cell belongs to exactly one white island. The number tells you the exact count of white cells that island must contain. A cell showing “3” belongs to an island of exactly three white cells connected side to side. A cell showing “1” is already a complete island of one.
Rule 2 — Islands never touch side to side. Two separate white islands cannot share a horizontal or vertical edge. Diagonal neighbors are fine — islands can touch at corners — but side-by-side contact is forbidden. The black sea must separate every island from every other on all sides.
Rule 3 — The sea is one connected group. All black cells must form a single, connected region. You cannot end up with isolated patches of black cut off from the main body of sea.
Rule 4 — No 2×2 black pools. No block of four black cells arranged in a 2×2 square is allowed. This rule keeps the sea irregular and flowing rather than filling up in solid chunks.
The natural entry point on any Nurikabe grid is the “1-cell island”: any numbered cell showing “1” is a complete island by itself, so all four of its orthogonal neighbors are immediately black. Similarly, any cell so far from all numbered cells that no island could plausibly reach it is sea. From these anchors, the constraints begin to cascade outward across the grid.
Nurikabe rewards both local reasoning (counting cells toward an island’s clue) and global checking (confirming the sea stays connected, watching for pool formation). That combination — local counting plus global connectivity — is what gives the puzzle its distinctive feel.
For a step-by-step solving walkthrough, How to Solve Nurikabe covers beginner strategies in full.
What Is Hitori?
Hitori was also published by Nikoli — their magazine’s March 1990 issue, one year before Nurikabe — according to Wikipedia’s Hitori article. The name translates roughly as “leave me alone” or simply “alone,” a fitting label for a puzzle whose entire purpose is to isolate each number until every row and column holds no duplicates.
Unlike Nurikabe, Hitori starts with a completely full grid. Every cell already contains a number. You do not add anything; you shade cells dark to remove them from consideration. Conceptis Puzzles, one of the main publishers of Hitori, states the three rules as:
Rule 1 — No repeats in a row or column. Among the unshaded (white) cells in any row or column, each number may appear at most once. If the number 4 appears twice in the same row, at least one copy must be shaded out.
Rule 2 — Shaded cells never touch side by side. Two shaded cells cannot share a horizontal or vertical edge. Diagonal contact is fine, but side-by-side adjacency between shaded cells is always illegal.
Rule 3 — All white cells must stay connected. When you finish the puzzle, every unshaded cell must be reachable from every other unshaded cell by moving through white cells only. No isolated white region is allowed.
Three rules pull against each other productively. Rule 1 pushes you to shade duplicates; Rules 2 and 3 constrain where and how many you can shade. The tension between them is where all the interesting logic happens.
The two entry patterns that make Hitori click quickly are the Pair (two identical numbers directly adjacent in a row or column — at least one must stay white, claiming that number, so every other copy in that row or column is shaded) and the Sandwich (identical numbers flanking a different number in a line — the middle number is always confirmed white, because shading it would force both flanking copies to stay, repeating a number). Neither pattern requires guessing. Both give you a forced deduction you can immediately act on.
Hitori has no fixed grid size. A 5×5 grid is a comfortable start; standard published grids often run to 8×8 or larger. The rules never change — only the number of cells and the density of constraints.
For the solving strategies in full detail, How to Solve Hitori covers both entry patterns and the common mistakes to avoid.
Nurikabe vs Hitori: The Key Differences
Both puzzles come from the same publisher, use shading, and require that certain cells form connected regions. Everything else differs.
| Dimension | Nurikabe | Hitori |
|---|---|---|
| Starting state | Mostly blank — a few numbered cells, the rest empty | Completely full — every cell already has a number |
| What numbers mean | Island size: exact count of white cells in that island | Values to de-duplicate across rows and columns |
| What you decide | Which blank cells become white (island) vs. black (sea) | Which numbered cells to shade dark (eliminate) |
| Shading goal | Paint the sea so islands have exact correct sizes and separation | Eliminate duplicates so no number repeats per row or column |
| Constraint on shading | No 2×2 pool of black; sea must all connect | Shaded cells cannot touch side by side |
| Constraint on unshaded cells | Islands must match clue exactly; islands cannot touch | No repeat per row/column; all white cells connected |
| Number of rules | 4 | 3 |
| Scale of reasoning | Global — island sizes and sea connectivity span the whole grid | Local to global — entry patterns are self-contained; chains propagate outward |
| Closest relative | Territory/region puzzles, crossword-layout logic | Elimination puzzles, Sudoku-adjacent row-column logic |
| Origin | Nikoli, 1991 | Nikoli, March 1990 |
The sharpest single difference: in Nurikabe, numbers are clues that shape regions; in Hitori, numbers are the content you are cleaning up. Both puzzles use shading, and both have a connectivity rule — but they point in opposite directions. Nurikabe’s connectivity rule governs the black sea; Hitori’s governs the white cells. Nurikabe’s shading constraint is about pools; Hitori’s is about adjacency between shaded cells. Even the overlap is a surface resemblance.
Which Is Easier to Learn?
For most beginners, Hitori is the more accessible starting point.
Hitori has three rules versus Nurikabe’s four. More importantly, its two entry patterns — the Pair and the Sandwich — are easy to learn in one sitting and give you an immediate, forced first move on any grid. A beginner on a 5×5 Hitori can typically find several moves in the first two minutes without guessing, and the logic stays close to the initial scan for a while before connectivity becomes the main challenge.
Nurikabe’s learning curve feels steeper not because any single rule is harder, but because all four rules interact from the very beginning. You are counting island cells, checking for pool formation, and verifying sea connectivity often at the same time. The “1-cell island” shortcut and the “far-from-all-clues = sea” heuristic help, but beginner Nurikabe grids tend to require more patience before the solution starts to crystallize.
The sticking points in each puzzle are also different in character:
In Hitori, solvers get stuck most often because they missed a Pair or Sandwich in the initial scan, or forgot to mark the four neighbors of a newly shaded cell as white. The error is local — usually a single pattern that was overlooked early, which compounded. Backtracking is straightforward: find the missed pattern, apply it, propagate the chain.
In Nurikabe, solvers get stuck most often when an island’s growth direction becomes genuinely ambiguous — the count is tracking correctly, but you are not sure which cells the island should extend into without violating Rule 2 (islands touching) or Rule 4 (pool formation). These stalls often require checking the global connectivity of the sea rather than just the local island neighborhood. The fix takes more of the grid into account.
Neither puzzle requires arithmetic. Both are pure deductive logic — no memory for vocabulary, no calculation beyond counting. If you find row-and-column scanning natural (as in Sudoku), Hitori will feel familiar quickly. If you find spatial reasoning and territory division more interesting, Nurikabe’s learning curve is worth the investment.
On small grids, both puzzles are genuinely approachable in one short session. Most people who enjoy one eventually try the other.
Which Should You Try?
The most reliable guide is what kind of thinking you find satisfying — not any external ranking of difficulty or mental benefit. Both puzzles are genuinely engaging for the right person.
Start with Hitori if:
- You enjoy Sudoku or other row-and-column logic puzzles and want a different flavor in the same category.
- You prefer puzzles where entry moves are visible without scanning the entire grid at once.
- You want to finish your first puzzle in 10 to 15 minutes rather than settling into a longer session.
- You like the satisfying snap of a forced deduction — “that cell must be shaded, there is no other valid option.”
- The idea of eliminating possibilities from a full grid feels more intuitive than building regions from scratch.
Start with Nurikabe if:
- You like spatial puzzles: dividing territory, shaping regions, growing islands in specific directions.
- The idea of a mostly blank grid that you fill in by reading size clues sounds more interesting than scanning a cluttered grid for duplicates.
- You enjoy crossword-layout puzzles or maze-like logic where the final shape of the solution matters as much as what it contains.
- You are already comfortable with Hitori and want something that asks you to track more constraints simultaneously.
On difficulty by grid size: both puzzles scale cleanly. A 5×5 version of either is a solid entry point — enough cells to have real decisions, few enough not to be overwhelming. A 10×10 Nurikabe or Hitori is a genuinely substantial session. The rules themselves do not change as the grid grows; only the density of constraints and the depth of deduction chains increase.
On playing both: some solvers work through one Hitori and one Nurikabe in the same session, alternating between them. The local scan-and-eliminate pace of Hitori and the region-building pace of Nurikabe complement each other in a way that can keep the overall experience fresh. Switching between them during a break feels like shifting gears rather than starting over.
On the broader question of cognitive engagement: solving puzzles you find genuinely enjoyable is a pleasant way to spend time with number sense and spatial logic. Research on specific benefits of individual puzzle types tends to be task-specific, and neither puzzle promises a particular outcome beyond the enjoyment of solving it.
A Free Puzzle to Try Right Now
If the Hitori side of this comparison caught your attention — the mechanic of looking at a grid full of numbers and choosing which cells to remove — Clear Sum works from the same starting point.
In Hitori you shade cells so no number repeats in any row or column. In Clear Sum, you click cells to delete them so every row and column hits a target sum. The mechanic is the same: a filled number grid, cells removed according to a row-and-column rule, pure logic to find which ones go.
Clear Sum is free in your browser — no download, no account, no time limit.
Frequently Asked Questions
What is the main difference between Nurikabe and Hitori?
The starting condition is the clearest difference. Nurikabe starts with a mostly blank grid where a handful of cells contain numbers — those numbers tell you the exact size of the white island that must surround them. Hitori starts with a grid completely filled with numbers — your job is to shade some cells dark until no number repeats in any row or column. In Nurikabe, numbers are clues that tell you how large to make each island. In Hitori, numbers are the content you are sorting and eliminating. Both puzzles use a connected-region rule — Nurikabe’s applies to the black sea; Hitori’s applies to the remaining white cells — but they are otherwise mechanically distinct.
Which is easier to learn, Nurikabe or Hitori?
Hitori is generally the more accessible starting point. It has three rules (no repeats per row or column; shaded cells cannot touch side by side; all white cells stay connected) versus Nurikabe’s four (island size matches clue; islands cannot touch; sea stays connected; no 2×2 black pool). More usefully, Hitori has two named entry patterns — the Pair and the Sandwich — that give beginners a clear, forced first move on any grid. Nurikabe does have entry shortcuts (the 1-cell island, cells too far from all clues to be anything but sea), but the interaction of its four rules requires tracking more things at once from the start. On a small grid, both puzzles are approachable in one session. On a larger grid, Nurikabe typically demands more patient enumeration before the solution crystallizes.
Are Nurikabe and Hitori related to Sudoku?
All three are grid logic puzzles with no arithmetic — no multiplication, no calculation beyond basic counting — and all three originated in Japan, popularized by Nikoli. Sudoku fills an empty grid with digits using placement logic; Nurikabe and Hitori both use shading rather than filling. Hitori’s Rule 1 (no number repeats in a row or column among white cells) is closest in spirit to Sudoku’s core constraint, though Hitori reaches uniqueness by elimination while Sudoku reaches it by placement. Nurikabe’s region-building logic is less like Sudoku and more like territory puzzles. All three belong to the broader family of grid deduction puzzles — logic puzzles for adults maps how they relate.
Where can I play Nurikabe and Hitori for free?
Both puzzles have free browser-based versions from several publishers — searching “free Nurikabe puzzle” or “free Hitori puzzle” returns options that need no download and no account. Nikoli, the original publisher of both, provides puzzle information at nikoli.co.jp; Conceptis Puzzles publishes online versions of Hitori and other Nikoli-style puzzles. Starting with a 5×5 or 6×6 grid in either puzzle gives you a complete experience of the rules without the cell count becoming overwhelming. If you want something to try right now while the comparison is still fresh, Clear Sum is a free number-grid puzzle on this site — you click cells to remove them until every row and column hits a target sum, which uses the same deletion mechanic as Hitori’s shading step. No sign-up, runs in your browser.
Just for fun — not medical advice.
Keep reading
More from the Make10s blog: how to solve Nurikabe · how to solve Hitori · logic puzzles for adults · KenKen vs Kakuro · brain games like Sudoku · all posts
Sources: Nurikabe — Wikipedia (Nikoli 1991, name folklore etymology, four rules) · Nikoli Nurikabe page (official publisher rules) · Hitori — Wikipedia (Nikoli March 1990, name meaning “leave me alone”) · Conceptis Puzzles Hitori rules (three-rule formulation).
Just for fun — not medical advice.