In Shikaku the whole grid is divided into numbered rectangles. In Nurikabe you shade cells to form one connected “wall”; the unshaded cells form islands, each containing exactly one number equal to its size, and the wall may not contain any 2×2 block.
Side by side
| Shikaku | Nurikabe | |
|---|---|---|
| Regions | Rectangles covering everything | Islands of any shape + one wall |
| Every cell numbered region? | Yes | No — wall cells belong to no island |
| Connectivity rule | — | All shaded cells connected |
| Extra rule | — | No 2×2 shaded block |
| Publisher | Nikoli | Nikoli |
In detail
Nurikabe adds two global rules — wall connectivity and the 2×2 ban — that make it feel very different from Shikaku’s local rectangle logic. Both, however, reward the same habit: asking which numbers can reach a given cell.
Which should you play?
Shikaku has simpler rules and is quicker to learn. Nurikabe is a great follow-up for solvers who enjoy reasoning about connected regions.
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Questions
Is Nurikabe similar to Shikaku?
Partly: in both, numbers give region sizes. Nurikabe regions can be any shape and are separated by a connected shaded wall.
Which is harder, Nurikabe or Shikaku?
Nurikabe is usually considered harder to learn because of its connectivity and 2×2 rules.