Bubble Sudoku › Guides

6 Common Sudoku Mistakes

Almost every spoiled puzzle comes down to one of six small slips, with numbers or colors. Each one is easy to fix once you know to look for it.

1. Guessing

   A guess feels like progress, but one wrong bubble quietly breaks every move built on it, and you won’t find out until the board stops making sense. Sudoku never needs a guess. If you’re truly stuck, test a color in a way you can take back.

   Lesson: Test a Bubble

2. Forgetting the block

   It’s easy to check a cell’s row and column and stop there. Here Dark Green fits its row and its column, but the block already has one in its top-left corner. Every move needs all three checks: row, column and block.

   More: The Rules

3. Writing notes you can’t prove

   Notes only work if every dot is a color the cell can really hold. Writing all nine “just in case” hides the real moves. Write a dot only after checking the cell’s row, column and block.

   Lesson: Notes

4. Leaving old notes behind

   When you place a color, its dot has to come off every other cell in that row, column and block. Here Dark Green was just placed, but the cell beside it still shows a Dark Green note. Old dots point you at moves that aren’t there. Bubble Sudoku clears them for you, unless you turn that off in Settings.

   Lesson: Obvious Single: With Notes

5. Scanning only rows

   Many players read the board left to right like a page and miss what the columns and blocks are showing. Follow one color across the whole board instead. It finds moves in every direction at once.

   Lesson: Hidden Single: Last Remaining

6. Staring at one corner

   When one area stops giving answers, it usually stays stuck until something changes elsewhere. Move on to another part of the board, then come back. Every bubble you place somewhere else can open up the corner you left.

   More: What to try when you’re stuck