Shuttle islands [Nurikabe U-Bahn Bridges 13x14]
(Published on 16. January 2024, 01:00 by Christounet)
After I made my first U-Bahn hybrid, I wanted to explore further with some other hybrid. This puzzle is vaguely inspired by 2 puzzles from Nell Gwyn, who experimented a nurikabe / bridges hybrid. It seemed very natural to connect all the bridges with a U-Bahn network. I modified the usual bridge rule a bit, allowing bridges to cross, to create a new layer of logic. Testing feedback estimated a solid 4* difficulty, maybe 5*. I hope you enjoy !
The puzzle :
Play on Penpa (answer check with grey shading for the water, and green lines for U-Bahn)
Rules :
- Standard U-Bahn : Draw a loop network through the centers of some cells, which may branch or turn, but may not have any dead ends. Clues to the left and above the grid indicates how many times the corresponding line shape (i.e. a cross, branch, straight line, or turn) appears in the corresponding row or column, irrespective of the line shape's rotation.
- Nurikabe : Shade some cells in the grid so that all shaded cells (water) are orthogonally connected, and no 2x2 area may be entirely shaded. Unshaded cells form groups of orthogonally connected cells (islands).
- Bridges : Some islands are connected to other islands by bridges. A bridge must go straight from a cell on one island to a cell on another island. Bridges cannot turn or branch, but they may cross one another. They cannot start or end on the same cell as another bridge. All bridges are part of the U-Bahn network. In water cells, there cannot be any U-Bahn cell that is not part of a bridge.
- Clues : All clued cells in the grid are part of islands. A clue can either be the size of that island or the number of bridges connecting that island to other islands. If a cell contains 2 clues, one of them is the island size, the other one a number of bridges. Each island has at least 1 clue indicating its size, and at most 2 clues (indicating its size and number of bridges). A ”?” represents any digit from 1-9.
Example puzzle :
Here are examples of forbidden patterns of U-Bahn network in the water cells :
Solution code: For each row except the last, from top to bottom, the number of lines leading down from that row
Comments
on 22. February 2024, 16:37 by Silverstep
Rules clarification: Can the middle cells of a "bridge" be land cells? I'd think they all have to be water, but it's not mentioned anywhere.
Example image: https://imgur.com/a/vn2DXeL
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@Silverstep : In your example, you have to consider that there are 2 separate bridges. I will try to reformulate this so that it is clearer in the rules.
on 6. February 2024, 08:03 by Statistica
Wow. Very hard until the last line :-)
on 26. January 2024, 13:25 by Piatato
Excellent ruleset, particularly in the way it makes so much realistic sense! Unfortunately I overlooked something quite simple for two-three days in the midsolve, but I can only blame myself. Awesome stuff!
on 24. January 2024, 22:17 by Myxo
Such an intricate combination of rules, leading to pure beauty!
on 20. January 2024, 07:50 by Christounet
Updated estimated difficulty based on feedback.
on 18. January 2024, 01:40 by Sewerin
Great puzzle with a very satisfying start
on 17. January 2024, 00:06 by ONeill
Very cool :)
on 16. January 2024, 12:08 by Jesper
Awesome combination, thanks!
