Solo / Sudoku
Do diagonals count in Solo Sudoku?
In ordinary Solo, digits must be unique in each row, column and block. Diagonal uniqueness is an extra rule enabled by the X option, not a rule of the default puzzle.
Worked example
A repeated digit along a diagonal can be legal in the default mode if its cells occupy different rows, columns and blocks.
What to check on your board
Apply the rule above to your current board, then verify the remaining puzzle constraints. The example explains a local deduction; it is not a solution to every randomly generated board.
Checking your next move
For a doubtful digit, inspect its row, column and block in turn. Remove candidates only when one of those constraints rules them out. Check the puzzle options before adding a diagonal restriction; applying a rule from another Sudoku variant can remove a perfectly legal candidate.
Using this reference
For Solo / Sudoku, read the rule and the worked example together before opening the game. Separate what the rule explicitly requires from what only seems likely on the current board. A useful next move is one you can explain from the visible constraints, not merely a pattern that looks familiar.
If you get stuck, isolate a smaller part of the position and list what is still possible there. After a move, check the affected rows, regions or connections again. The reference explains the documented rules; progress, controls and save behavior belong to the linked game.
Read the developer’s manual ↗ · Open the developer’s browser version ↗
Manual inspected: · Simon Tatham & contributors · MIT