Strategy Detailed Descriptions Strategy Detailed Descriptions You need to mark which digits are impossible in each unsolved cell before using advanced strategies. These strategies do not directly solve a cell, but can mark more digits impossible which can lead to more solutions by easier strategies.
More sophisticated strategies (e.g. "Xwing", "Swordfish", "Ywing", etc.) can be found beyond what this program currently implements. The diligent solver can become smarter than the computer by researching these and putting them to use. See Resources to learn more about these.