Learn
The techniques, one at a time
Each technique: its explanation, a demo, three puzzles where you'll spot it, with a coach reasoning right along with you. Puzzles change every day.
Beginner
1 technique
Easy · Medium
1 technique
Hard
4 techniques
Pointing Pair
Inside a box, a digit can only sit on one row (or column).
Demo · 3 puzzles →
Claiming Pair
On a row or column, a digit can only land inside one box.
Demo · 3 puzzles →
Naked Pair
Two cells in the same zone share exactly the same two candidates between them.
Demo · 3 puzzles →
Hidden Pair
Within a zone, two digits can only go in two cells.
Demo · 3 puzzles →
Expert
5 techniques
Naked Triple
Three cells in the same zone share only three possible digits between them — not necessarily all three in every cell.
Demo · 3 puzzles →
Hidden Triple
Within a zone, three digits can only occupy three cells.
Demo · 3 puzzles →
Naked Quad
Four cells in the same zone share only four possible digits between them.
Demo · 3 puzzles →
Hidden Quad
Within a zone, four digits can only occupy four cells.
Demo · 3 puzzles →
X-Wing
A digit is only possible on two rows, and on each of those rows only in the same two columns.
Demo · 3 puzzles →
Extreme
4 techniques
XY-Wing
A pivot cell with two candidates {A, B} sees two wings: one holds {A, C}, the other {B, C}.
Demo · 3 puzzles →
XYZ-Wing
An extension of the XY-Wing: the pivot has three candidates {A, B, C}, and its two wings hold {A, C} and {B, C}.
Demo · 3 puzzles →
Swordfish
The X-Wing stretched to three rows and three columns: a digit can only occupy those three columns across those three rows, whatever the exact split.
Demo · 3 puzzles →
Jellyfish
The X-Wing stretched to four rows and four columns.
Demo · 3 puzzles →