Zippular Cities
(Published on 30. July 2025, 11:41 by gdc)
This weeks setting challenge was about zipper lines and skyscrapers. I decided to use a "weaker" version of zipper lines (by heliopolix) instead to give the skyscrapers more spotlight. Thanks to the CtC fan discord for testing. Hope you enjoy!
Zippular Lines: Each pair of digits an equal distance from the central spot on a Zippular line have the same SUM MODULO 3 (the remainder when the digits are summed and then divided by 3). The digit in the central spot has the same remainder when divided by 3. For example, 658 is a valid Zippular line, because 6+8=14, and 14 and 5 have the same remainder (2) when divided by 3.
Skyscraper Centers: A digit on a zipper center counts the number of digits seen when travelling from the center to one of its ends (excluding itself). A digit is seen if it is larger than all the digits before it. Both arms must result in the same count.
Visual Example
A valid fill for the bottom-right line. The "seen" cells for the skyscraper are highlighted. There are two seen cells on each arm counted by the digit 2 in the center. The mod 3 remainder of all "zipper sums" is 2 (7+1,4+7,9+5,8+3).
Solution code: The leftmost column, top to bottom (9 digits)
Comments
on 30. July 2025, 23:10 by wuc
Amazing puzzle. Great constraint combination. A bit of number theory helps. Great setting. 3* to me. Great fun thx.
on 30. July 2025, 20:49 by Exigus
Seemed like too many options at first but it was really fun to whittle them down. Thanks!
on 30. July 2025, 15:07 by heliopolix
Fun puzzle!
on 30. July 2025, 12:44 by gdc
update visuals
