Island Sum Lines
(Published on 1. November 2025, 00:22 by yttrio)
Rules:
Normal Sudoku rules apply.
Nurikabe:
-- Shade some cells such that all shaded cells are orthogonally connected (water), but no 2x2 area is entirely shaded.
-- Groups of orthogonally connected unshaded cells form islands. An island may be of size 1. Every cell with a circle clue is unshaded, and each island contains exactly one circle cell. The digit in this circle cell gives the size of the island. Note that an island may occupy a full 2x2 area (unlike water).
Digits may not repeat within an island.
Every blue line must contain at least one shaded and at least one unshaded cell. Switching between shaded and unshaded cells divides each line into segments with the same sum. Different lines may have different sums. Digits may repeat on a line if allowed by other rules.
6x6 Example:
The image below shows a sample 6x6 puzzle and solution with the same rule set.
Play the example 6x6 in SudokuPad.
Solution code: Shaded (water) cells in row 5 from left to right
Comments
on 8. November 2025, 05:34 by alanb
I got trapped on an island. Fortunately I was able to swim to safety once I remembered all the rules.
on 7. November 2025, 16:30 by Klausku
Beautiful puzzle with a very nice combination of rules. Thanks.
on 7. November 2025, 10:46 by Klausku
Beautiful puzzle with a very nice combination of rules. Thanks.
on 3. November 2025, 21:22 by Agent
Great fun! I liked the diagonal connectivity deduction.
on 3. November 2025, 11:09 by Titus Adduxas
Gorgeous puzzle. Brilliant logic throughout. Thanks.
on 2. November 2025, 09:34 by Titus Adduxas
Gorgeous puzzle. Brilliant logic throughout. Thanks.
on 2. November 2025, 00:53 by Elker
Very fun puzzle as always. Thanks for setting.
on 1. November 2025, 21:14 by Calvinball
On an island in the sum, we'll be playing and having fun, and it makes me feel so fine, I can't control my brain.
on 1. November 2025, 17:57 by wuc
Brilliant. I havent solved many Nurikabes. To me 4*. Hard tricky rewarding and great fun thx.
on 1. November 2025, 16:01 by giladooshlon
Great puzzle. 2-3* most of the way except for the crux finale.
on 1. November 2025, 15:35 by sujoyku
Incredible puzzle! Especially the ending did take all of me. Thank you, yttrio!
on 1. November 2025, 12:34 by Snookerfan
Fabulous puzzle! Nurikabe is such a great genre and this is a great hybrid full of clever deductions. A joy to solve, thank you
on 1. November 2025, 11:57 by Franjo
Absolutely amazing, from the nice break-in up to the last island cell! Thank you very much for creating and sharing this beautiful Nurikabe-hybrid.
on 1. November 2025, 11:56 by thrutch
That was excellent. I got very stuck for an embarrassingly long time at a point where I couldn't make use of a slightly tricky deduction I'd made due to missing a much more obvious fact that I'd been ignoring for some time. Once the light dawned the rest of the puzzle solved as smoothly as everything up to that point.
