This puzzle was created by Jakhob and wooferzfg, and it is a combination of a U-Bahn and a Coral. It was inspired by KNT's Siamese Coral and Zzzyxas's Cave U-Bahn.
If you are unfamiliar with U-Bahn, here is a guide that covers the core logic.
Shade some cells so that all shaded cells form one orthogonally connected area and the unshaded cells are all connected orthogonally by other unshaded cells to the edge of the grid. No 2x2 region may be entirely shaded.
Draw a loop network through the centers of some unshaded cells, which may branch or turn, but may not have any dead ends.
A clue outside the grid on the left or top 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.
Clues outside the grid on the bottom and right represent the lengths of the blocks of consecutive shaded cells in the corresponding row or column, written in ascending order. A “?” can represent any non-zero value.
Solution code: For each row except the last, from top to bottom, the number of lines leading down from that row
on 29. May 2024, 03:21 by zzw
Amazing puzzle!! Such a good combination of rules, and lots of fun all the way through. Took me a long time to spot the break-in, and some other steps too, but they all turned out to be quite interesting.
on 12. February 2024, 14:04 by Christounet
You two keep making these wonderful U-Bahn hybrids ! Just awesome. Thanks :)
on 2. May 2023, 11:36 by Piatato
Fabulous puzzle! Great logic throughout!
on 1. April 2023, 12:43 by Zzzyxas
Nice combination. Thanks for being a source of inspiration.
on 27. March 2023, 02:40 by Xendari
Lovely! Found it quite challenging but I really liked the subway logic in this one.
on 26. March 2023, 23:53 by polar
Brilliant puzzle thanks!
on 26. March 2023, 23:00 by KNT
Really fun! Some of the early deductions after the break in sequence are seriously awesome.