4321-Bahn (ft. Christounet)
(Published on 14. March 2026, 00:00 by cyddrdrd)
This puzzle is created by Christounet and rdrd. Our previous collab puzzles can be found here, here and here.
Inspired by the fantastic and insane Thalassophobia by SamuPiano, I came up with a similar idea: empty cells within the same region contain the same number. We are very happy with the final result, which should be much more approachable than Thalassophobia (though still a bit challenging). Expected difficulty is around 5★, but may lower to 4★ if you are a U-Bahn expert. Feel free to reach out on Discord or leave a hidden comment if you'd like a hint. Enjoy!
Penpa+ (with solution check)
SudokuPad (no solution check)
Example puzzle:
We strongly recommend trying the example first to get familiar with the ruleset.
SudokuPad (example)
Inspired by the fantastic and insane Thalassophobia by SamuPiano, I came up with a similar idea: empty cells within the same region contain the same number. We are very happy with the final result, which should be much more approachable than Thalassophobia (though still a bit challenging). Expected difficulty is around 5★, but may lower to 4★ if you are a U-Bahn expert. Feel free to reach out on Discord or leave a hidden comment if you'd like a hint. Enjoy!
Rules
- Draw a totally connected loop network through the centers of some cells, which may branch or turn, but may not have any dead ends.
If a cell is part of the network, its number is determined by its line shape (irrespective of rotations): corner = 1, straight line = 2, branch = 3, cross = 4. - Empty cells form orthogonally connected regions. Different regions don't share an edge. An empty cell's number is equal to the size of its region, and must not be larger than 4.
- A clue outside the grid indicates how many times the corresponding number appears in the corresponding row/column.
SudokuPad (no solution check)
Example puzzle:
We strongly recommend trying the example first to get familiar with the ruleset.
SudokuPad (example)
Solution code: For each row except the last, from top to bottom, the number of lines leading down from that row
Last changed on -
Solved by Christounet, Piatato, Bellsita, tuturitu, Paletron, Rickium, Agent, kays, NEWS, Mr_tn, Jesper, Silverstep, CutieRainbow, ns08
Comments
on 31. March 2026, 21:10 by Jesper
Fantastic, thanks!
on 16. March 2026, 02:47 by Agent
That was wild, thanks!
on 14. March 2026, 00:04 by Bellsita
Crazy puzzle!
on 14. March 2026, 00:03 by Christounet
Very happy to have taken part in the creation of this puzzle! Looking forward to the next :)
on 14. March 2026, 00:02 by Piatato
Terrific puzzle!
