Today I learned that it’s possible to have a uniquely solvable Sudoku without numbers. Technically speaking one could argue whether it’s still a Sudoku or just a number puzzle, but the puzzle has the general form of a sudoku and just needs 3 additional rules to make it difficult but uniquely solvable.

I came across this, when checking out a video of the the YouTube channel “Cracking The Cryptic” about solving a similar puzzle with just 1 digit in it. Which then end up recommending me a video with no digits inside, just amazing.