I have unexplainable idiosyncracies even while playing sudoku.
I write the numbers in with a pen instead of a pencil, so I can practise to be precise rather than hazard wild guesses.
I can only tolerate black ink and no other colour.
I start a puzzle by randomly opening the book to an undone page, rather than follow the puzzle book sequentially.
And I have unfinished puzzles scattered throughout the book because I keep losing the page of the previously uncompleted ones.