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What Is Norinori?

Norinori is a binary-determination logic puzzle first published by the Japanese puzzle company Nikoli. The name comes from the Japanese onomatopoeia for “painting” or “sticking”. It sits in the same family of shading puzzles as Nurikabe, Heyawake, and LITS, but its rules are refreshingly simple while still offering deep logical challenge.

A rectangular grid is divided into regions (also called “rooms” or “areas”). Your task is to shade (colour) cells so that two constraints are satisfied: each region contains exactly two shaded cells, and every shaded cell is orthogonally adjacent to at least one other shaded cell — meaning every shaded cell is part of a domino (a 1×2 or 2×1 block of shaded cells).

Rules of Norinori

1. Two per region: Every region must contain exactly two shaded cells. No more, no fewer.
2. Domino constraint: Every shaded cell must be orthogonally adjacent to exactly one other shaded cell, forming dominoes — 1×2 or 2×1 blocks of shaded cells.
3. No adjacent dominoes: Dominoes may not touch each other orthogonally (horizontally or vertically). Diagonal touching is allowed. Each shaded cell has exactly one shaded neighbour — its domino partner.
4. Cross-region dominoes: A domino can span two different regions. Each region still needs exactly two shaded cells, but those two cells do not have to be adjacent to each other within the same region as long as each one is part of a domino (possibly with a cell in a neighbouring region).

Notice there is no connectivity requirement for all shaded cells globally — unlike Nurikabe or LITS, the dominoes do not need to connect to each other. The puzzle is about satisfying the two-per-region, domino pairing, and domino separation constraints.

How to Solve Norinori — Strategy Tips

1. Two-Cell Regions Are Free

If a region contains exactly two cells, both must be shaded. This is the most basic deduction and often gives you several dominoes immediately. Look for two-cell regions first — they are guaranteed starting points.

2. Domino Forcing in Small Regions

In a three-cell region (e.g. an L-shape or a straight line of three), you must shade exactly two of the three cells. Whichever two you pick, they (or at least one of them) must be adjacent to another shaded cell — possibly from a neighbouring region. Look at which cells in the region border already-shaded cells or forced positions in adjacent regions.

3. Look for Isolated Cells

A cell that has no shaded neighbour possible cannot be shaded. If all four orthogonal neighbours are either empty (cannot be shaded without violating some region's two-cell limit) or outside the grid, that cell must stay unshaded. This eliminates candidates in larger regions.

4. Propagation From Forced Dominoes

Once you place a domino that includes one cell of a neighbouring region, that neighbouring region now has one of its two shaded cells determined. The second shaded cell must also form a domino pair — work outward from each forced placement.

5. Parity and Counting

Since every shaded cell must pair into a domino, the total number of shaded cells is always even (it equals twice the number of regions). You can use counting arguments: if a region has exactly one candidate cell left for its second shaded position, that cell is forced.

6. Domino Separation

Remember that dominoes cannot touch each other orthogonally — only diagonally. If shading a cell would cause two different dominoes to become orthogonally adjacent, that placement is impossible. Use this constraint aggressively: once a domino is placed, every cell orthogonally adjacent to it (that isn’t part of the same domino) must stay unshaded. This often eliminates many candidates in neighbouring regions.

Grid Sizes & Difficulty Levels

• 6×6 — Easy: A compact grid with many small regions (often two or three cells each). Ideal for learning the rules. Typical solve time: 1–3 minutes.
• 6×6 — Medium/Hard: Same grid size but larger, more complex regions requiring longer deduction chains.
• 8×8: The classic Norinori experience with more regions and trickier interactions. Expect 3–8 minutes.
• 10×10: Large grids for experienced solvers. Many regions, intricate domino interactions, and satisfying “aha” moments. Can take 5–15 minutes.

Norinori vs Other Shading Puzzles

• vs Nurikabe: Nurikabe requires a single connected “sea” of shaded cells with numbered island clues. Norinori has no connectivity requirement — shaded cells just need domino pairs, and every region has exactly two.
• vs Heyawake: Heyawake shades cells in rectangular rooms with numbered clues, no-adjacency constraints, and a three-room rule. Norinori requires adjacency (dominoes) and has no numbered clues — just two per region.
• vs LITS: LITS places tetromino shapes inside regions. Norinori places dominoes. Both use region partitions, but the shape constraints differ significantly.
• vs Hitori: Hitori shades duplicate numbers so no row/column has repeats and no two shaded cells touch. Norinori has no numbers and requires shaded cells to touch in pairs.

History of Norinori

Norinori was invented by Nikoli, the renowned Japanese puzzle publisher that also created Sudoku, Slitherlink, Masyu, and many other logic puzzle types. It first appeared in Nikoli’s Puzzle Communication magazine. The puzzle gained popularity in the international puzzle community through online puzzle platforms and logic puzzle competitions, where it is prized for its elegant, minimalist rule set.

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