About 22 to 26 givens. The deciding step usually works across a box and a line at once, removing a candidate from cells you were not looking at.
New at this level
- Pointing Pair — Inside a box the digit sits on one line only → erase it from that line outside the box
- Box/Line Reduction — Along a line the digit sits in one box only → erase it from that box outside the line
- Naked Triple — Three cells' candidates total three digits → erase those three from the rest of the unit
- Hidden Triple — Three digits' homes total three cells → erase every other candidate from those cells
All levels
- Easy · naked singles only
- Medium · up to hidden singles
- Hard · up to pairs
- Very hard · up to intersections and triples
- Expert · up to advanced techniques
- How sudoku difficulty is graded