Learn to spot the next move.
Each lesson turns one Sudoku technique into a repeatable method you can use on a real grid.
01Sudoku rules
Check a cell’s row, column, and 3×3 box before placing a number.
02Scanning
Find missing numbers by checking one row, column, or box at a time.
03Candidate notation
Write the possible numbers in empty cells and update them after every placement.
04Naked singles
Find and place the only candidate left in one cell.
05Hidden singles
Place a number when it has only one possible cell in a unit.
Keep learning from intermediate to expert.
Coaching opens the remaining lessons, interactive proofs, practice, and scheduled reviews.
06How to solve a whole grid
Choose a simple method, work across the whole grid, and restart after every change.
07Locked candidates
Use shared cells to remove a possible number from the rest of a row, column, or 3×3 box.
08Naked pairs
Use two matching two-candidate cells to remove candidates from the rest of a unit.
09Naked triples
Use three cells whose combined candidates are exactly three digits to clear those digits elsewhere.
10Naked quads
Reserve four digits in four cells, then remove those digits from the rest of the unit.
11Hidden pairs
Track two digits limited to the same two cells, then remove the notes hiding them.
12Hidden triples
Track three digits limited to the same three cells, then remove the other candidates there.
13Choose an essential method
Use visible signals to choose the simplest useful search and restart after each change.
14Skyscraper
Follow one digit through two strong links and remove it only where both roofs can see.
15Two-string kite
Connect one strong line link and one strong column link through their shared box.
16X-Wing
Match one digit’s two possible positions in two lines, then remove it along the crossing lines.
17Empty rectangle
Use a digit’s empty box intersection and a strong link to prove one distant elimination.
18Finned X-Wing
Use a finned X-Wing to remove a digit only where the base and fin logic both apply.
19XY-Wing
Follow both values of a two-candidate pivot and remove the result forced by either route.
20XYZ-Wing
Prove that one candidate stays in a three-cell pattern, then remove it only where all three cells can see.
21W-Wing
Connect matching pairs through a strong link, then remove the other digit from their shared peers.
22Coloring
Alternate one candidate through connected two-place links, then use where the colors meet or collide.
23Chains
Follow a path of two-candidate cells, then remove a candidate that the two ends rule out.
24How to choose the next technique
Use candidate signals to choose, complete, and leave a method search without guessing.
25Swordfish
Keep one digit inside three crossing lines, then remove it beyond the three-line pattern.
26Unique rectangles
Verify the four-corner swap, then remove the repeated pair only from the corner with extra candidates.
27Forcing patterns
Test each candidate in a small starting cell. Follow only forced moves. Keep a shared result.