On the Sudoku-Front: The easier part is done, I can analyze rows of numbers if they are valid (1-9) and if they are “ok”, which means they may contain 0s, but no number is used more than once. Do I go the brute force-approach first? I’m thinking to first collect all 0s and fill out the ones that only have one possible solution. Repeat until there are only 0s with multiple possible numbers left. This approach may finish very easy Sudokus. Then try out all kinds of combinations of possible numbers, until there is no “contradiction” left.