Patient Zeroes
(Published on 26. October 2025, 15:38 by gdc)
A Halloween puzzle inspired by the mountain sudoku variant. Thanks ViKingPrime for helping with the lore and aesthetic ideas. According to testers (thanks everyone!) this one should be on the higher end of 3 stars in difficulty. You can find an example puzzle below. Hope you enjoy!
Norma L. Dokes: Normal sudoku rules apply.
Infections: Each digit matching its box number is a "patient zero". Each row and column contains a "patient zero". Patient zeroes are infected. Infected cells infect every orthogonally adjacent cell with a smaller digit. Infections keep spreading until no infected cell has a smaller uninfected orthogonal neighbor. (Every infected cell can be traced back to one or more patient zeroes.)
Path: Draw a 1-cell wide path from the doctor to the hospital. The path only moves orthogonally and may not touch itself, not even diagonally. The path may not contain infected cells.
Microscopes are on the path and count the number of infected cells in the (up to 9) surrounding cells.
Kropki Tablets join consecutive uninfected digits.
Example Puzzle
A 6x6 example of the ruleset. Colors: Green for uninfected, red for patient zeroes and yellow for other infected cells. You can play the example here but the path of the 6x6 is not unique in box 2.
Solution code: Digits on the path in column 8, top to bottom.
Comments
on 10. November 2025, 20:37 by mscha
Wonderful new ruleset, I love the interaction between infections and microscopes.
This promises to be an epic series!
on 9. November 2025, 05:58 by silent_rob
Thanks for the amazing puzzle! Harder than those I usually attempt but the way the theming worked into the mechanics was so well done I had to give it a try. So glad I did because I really enjoyed it!
on 5. November 2025, 13:44 by Christounet
Epi(demi)c puzzle! Thanks :)
on 1. November 2025, 14:35 by sunevora
Beautiful puzzle!
Would have been faster if I had remembered one 'patient zero' per row and column.
on 1. November 2025, 12:08 by eladv
This was wonderful! I'm just re-solving the Rat Runs, and this gives me the same sense of beauty, but with totally different kind of logic. The inflection logic is really cool, and I wonder how far it can go. Some of the steps were really nice -- I guess I should go check out Mountain Sudoku! :)
on 29. October 2025, 19:04 by marcmees
Very original and nice. Thanks for sharing.
on 29. October 2025, 18:43 by Exigus
Perfect pathfinding puzzle. Hard but not too much. I totally forgot the "one per row and column" part for quite a bit but other than that fairly smooth. Thanks!
on 29. October 2025, 18:40 by LehanLehan
Tasty treat as always, thanks,gdc.
on 29. October 2025, 09:33 by SZCrow
Great puzzle. For me, usually gcd’s puzzle is harder than other’s puzzle with the same difficulty rate, but this one is particularly easy. Maybe a 2 star? IDK
on 29. October 2025, 01:52 by zardoz37
I found this brutally hard and I kept getting the infection logic wrong.
on 28. October 2025, 02:53 by Silverscree
This felt like an accurate depiction of avoiding getting sick during the term as a teacher!
on 27. October 2025, 09:22 by Bankey
Very satisfying to track the infections and lay out a path for Dr Dokes! Thanks, @ gdc for letting us help:).
on 27. October 2025, 07:48 by wuc
Wow amazing puzzle. One has to be very careful. Great logic. Looking forward for more. Great setting thx.
on 26. October 2025, 20:46 by PrudentLuck
I loved the contact tracing theme and logic! Very nice puzzle!
on 26. October 2025, 19:45 by Scorps
Wow, probably the hardest puzzle I've managed to solve! Really enjoyed this, thank you for sharing.
on 26. October 2025, 17:29 by Ratfinkz
Loved this, really fun some lovely logic! Beautiful puzzle!
on 26. October 2025, 17:14 by rameshsrivats
Terrific puzzle. Great fun
on 26. October 2025, 17:07 by Nightmare2805
That was great
on 26. October 2025, 16:49 by ChinStrap
Loved this!
on 26. October 2025, 15:43 by jakestilesowen
Neat puzzle! I especially like the infection logic and am curious to see if any more puzzles are set with it.
