Learn Sudoku
Choose a technique to learn what to look for and why it works.
Techniques
Naked Single
Place the only candidate left in a cell.
Hidden Single
Find the only home for a digit in one unit.
Locked Candidates
Use the overlap between a box and a line.
Naked Pair
Reserve two digits for two matching cells.
Hidden Pair
Reveal two digits limited to the same two cells.
X-Wing
Connect two matching candidate positions across two lines.
XY-Wing
Use three two-candidate cells in a Y-shaped pattern.
Swordfish
Extend fish logic across three lines.
Simple Coloring
Alternate colors through strong candidate links.
Logical Chain
Follow alternating strong and weak links.