Thermohaline (Nurikabe Thermo Sudoku)
(Published on 11. October 2022, 09:00 by Agent)
What if each Nurikabe island were its own Sudoku thermometer? After several weeks of experimenting with Nurikabe hybrids, I found that most of my ideas revolved around pseudo killer cages and/or directional clues. What I liked about thermos is that they provide a strong digit placement restriction, and the possible paths along a thermo give rise to an additional layer of geometric logic. I hope you will enjoy! I recommend trying the example puzzle first if you have some doubts about the ruleset.
Rules
- Normal sudoku rules apply.
- Shade some cells in the grid such that all shaded cells are orthogonally connected. No 2x2 area can be fully shaded.
- Groups of orthogonally connected unshaded cells form islands, which do not touch orthogonally, but may touch diagonally.
- Digits along a thermo must increase from the bulb end.
- Each island must contain exactly one large circle (bulb) and one small circle (tip). All circles must be unshaded.
- On each island, it must be possible to draw a non-branching thermo that visits every cell on the island, going from the bulb to the tip. Thermos can move orthogonally or diagonally. A thermo can cross itself.
Example Puzzle (6x6)
Main Puzzle (9x9)
Solution code: Column 2 (from top to bottom) then column 9 (from top to bottom)
Comments
on 27. March 2024, 22:37 by Piatato
Very cool!
on 28. November 2022, 10:50 by Christounet
Excellent puzzle ! Some hard deduction in the midsolve to get rid of some ambiguity, but very enjoyable all the way. Thanks
-- Thank you @Christounet! Admittedly this puzzle and especially the mid-solve is a bit evil.
on 28. October 2022, 23:52 by peacherwu2
Masterpiece! Very tricky yet beautiful crossover. Almost give up at the middle box.
-- Thanks @peacherwu2! I'm really glad to hear this.
on 26. October 2022, 18:38 by StephenR
Great stuff. Like some others, I failed to spot some configurations of thermos and broke the puzzle twice. Agent kindly gave me a hint which enabled me to solve it. Very neat idea which messes with your head!
-- Thank you @StephenR! Seems like it's very easy to overlook cases with this puzzle, but I'm glad you got there in the end!
on 19. October 2022, 02:12 by Xendari
I was a bit confused by the ruleset initially, but it ended up playing out quite intuitively. The interactions between islands were really fun to discover, and there was a lot of nice geometrical logic. Thanks Agent :)
-- Thank you @Xendari for the kind feedback! I see that you solved several of my puzzles lately, so thanks for that as well. I hope you had a great time with them!
on 18. October 2022, 11:59 by MartinR
That was very tricky and took me several goes, as I kept breaking it with a wrong assumption on a thermo branch
- had to leave it a few days to refresh, and today saw the option I'd incorrectly eliminated/missed
-- Sorry about that, I admit that the geometry of thermos is a bit evil. But I'm glad that you persevered and were able to solve it in the end!
on 15. October 2022, 23:26 by bansalsaab
Very nice puzzle. Crossing thermos definitely upped the difficulty but worth it.
-- Thank you @bansalsaab! I agree that the geometry of thermos is quite tricky in this puzzle.
on 14. October 2022, 10:36 by henrypijames
Great puzzle, recommend for CtC!
At first I didn't understand how a thermo could cross itself, but then I learned. :D I think showing a self-crossing thermo in the example puzzle would be very helpful.
I made a fatal mistake (unrelated to self-crossing) and had to restart. But even with that, the puzzle is only 4 difficulty for me.
-- Thank you @henrypijames! That's still harder than most puzzles ;) You're not the first person to point out that the possibility of crossing thermos was confusing, I'll keep this in mind.
on 12. October 2022, 08:21 by MagnusJosefsson
Very cool concept, and some really nice logic in this puzzle! At times quite difficult.
-- Thank you @MagnusJosefsson! It's probably one of my hardest puzzles so far, and very easy to miss some possibilities.
on 11. October 2022, 17:29 by Vebby
Excellent!
-- Thank you @Vebby!
on 11. October 2022, 13:03 by Snookerfan
Superb puzzle, really interesting how the shape of the islands evolved and how the thermo's where forced. Thank you so much!
-- Thank you @Snookerfan, glad to hear that you enjoyed the interactions between the rules!
