TOP SUDOKU HARD - HARD SUDOKU SECRETS

Naked and concealed singles are the easiest squares to resolve. A unadorned single is every time a quantity can only go in a single possible cell. A concealed single is when You can find only cell for a presented candidate.​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​�