The case notes
How fog of war works
Most clues start hidden. A correct placement reveals its three-by-three neighbourhood. Watch a worked example, then try the idea in a puzzle.
Put it into practice
Solve what you can see
Most of this Sudoku is hidden under fog. Only the clear cells can show their clues. We have one full row to work with.
The row needs 5
This row has one, two, three, four, then six through nine. Five is missing, so it belongs in the middle.
A correct digit clears fog
Place the five. It is correct, so the fog will clear around that cell and show us more of the puzzle.
A new clue appears
There it goes. The three-by-three area around our five is uncovered. A hidden two appears just above it.
Each correct step reveals more
Work from the visible clues. A correct placement clears its surrounding cells. A wrong guess leaves the fog in place.
Read the transcript
Most of this Sudoku is hidden under fog. Only the clear cells can show their clues. We have one full row to work with. This row has one, two, three, four, then six through nine. Five is missing, so it belongs in the middle. Place the five. It is correct, so the fog will clear around that cell and show us more of the puzzle. There it goes. The three-by-three area around our five is uncovered. A hidden two appears just above it. Work from the visible clues. A correct placement clears its surrounding cells. A wrong guess leaves the fog in place.
