Invisible Inkling

(Published on 11. March 2026, 15:35 by Timpanist)

Thanks for playing! - Tim

Normal 6x6 Sudoku rules apply.
I have drawn all possible white and black Kropki dots into the grid, as well as exactly one thermometer—but I used invisible ink!
Clues outside the grid indicate the first "invisible" feature seen from that direction (White dot, Black dot, or Thermometer cell).

For Reference:

White Dots: Border between two cells with consecutive digits.
Black Dots: Border between two cells with digits in a 1:2 ratio.
Thermometer: A single path of cells, connected orthogonally or diagonally, where digits strictly increase from one end to the other.

Note: A border between a 1 and a 2 may be marked with either a white dot or a black dot.

Example of how clues "see"

Play on SudokuPad

Solution code: Row 2, from left to right

Solved by StephenEsven, StefanSch, kublai, anton_anton, Yawnus, TeamSchmidt, dzamie, SKORP17, CheeseGarrison, juggler, marcmees, fkib, lars, pep9, Janie, Lithium-Ion, Brandonreider13, balpha, BakersDozenBagels, achim-t, eladv, dorverbin, OuyangZheng, lizaardvark

Full list

Comments

on 13. March 2026, 14:50 by Timpanist
Lithium-ion, my intention with that line is to indicate that if two cells “could” have a dot between them, then they “must”. Technically, it is a negative constraint, you just can’t see all the dots. I understand how usually that wording on a different puzzle would indicate otherwise.

on 13. March 2026, 12:18 by Lithium-Ion
I really struggled with the wording of the rule "drawn all possible white and black Kropki dots in the grid". I wrongly thought that this would imply a negative constraint on Kropki dots.

on 13. March 2026, 00:09 by pep9
Wonderful puzzle, really cool idea!

on 12. March 2026, 04:46 by Timpanist
Thanks everyone!

on 12. March 2026, 04:13 by juggler
Lovely puzzle!

on 11. March 2026, 16:30 by StefanSch
Interesting ruleset!