Hard Sudoku
Welcome to Hard Sudoku, where pairs and triples won't take you to the end. Every puzzle needs at least one pattern that spans the grid: a wing such as the W-Wing or XY-Wing, a single-digit pattern such as the Skyscraper, or a fish such as the X-Wing.
Techniques You'll Need
- X-Wing
When a candidate fits only two cells in each of two rows, and those cells sit in the same two columns, it can be eliminated from the rest of those columns
- Skyscraper and Two-String Kite
Single-digit patterns where two strong links are joined by one end of each, in the same row, column or box, so a cell that sees both of their other ends can't hold that digit
- XY-Wing and XYZ-Wing
A hinge cell sees two two-candidate wings that share a digit, and that digit goes from every cell that sees both wings (and, in an XYZ-Wing, the hinge too)
- W-Wing
Two cells with the same two candidates, joined by a strong link on one of them, so the other candidate can be removed from every cell that sees both
- Finned X-Wing
An X-Wing with one or two extra candidates in one box, its fin: it still removes the digit from the cells the X-Wing would clear that also see the fin
Advanced Challenge
These puzzles require careful analysis and the ability to spot complex patterns. You'll need to master multiple advanced techniques and often combine them in creative ways. Hard mode is where casual solving transforms into strategic problem-solving, requiring patience and methodical thinking.