SudokuIQ Practice Studio
A short daily exercise asks you to inspect one real Sudoku position, calculate every legal candidate, and compare your reasoning with the row, column and box evidence.
Today’s logic workout
Select every digit that can legally go in R8C8. Use its row, column and box—not the completed answer.
Candidate check · R8C8
Every empty square belongs to one row, one column and one 3x3 box. A digit is legal only when it is absent from all three. This exercise deliberately asks for every surviving candidate so you practise the complete check instead of spotting one attractive number and guessing.
If several candidates survive, the cell is not solved. That is useful information: record the candidates and move to another unit. A number becomes a placement only when a logical pattern proves it, such as a Naked Single or the only legal home in a unit.
One careful candidate audit each day improves scanning accuracy. The streak is stored only in your browser; no account or public profile is required. Follow the exercise with a live puzzle or open the Logic Lab when you want the same explanation for your own board.