Practise: X-Wing
This puzzle is picked so that the easy moves run out and exactly the X-Wing gets you going again. Solve as far as you can — when nothing obvious is left, the pattern is waiting for you.
Skip the obvious cells and start right where the technique is needed.
How to spot it
Choose a digit and find rows where it has exactly two candidate cells. Compare pairs of such rows: if their candidate columns match, you have an X-Wing. Repeat with columns to find the transposed version. Working one digit at a time across the whole grid is far more reliable than scanning visually.
Put it to use
Where you will meet it
Hard grids are built around moves like this one. That is where it earns its keep.
Play HardStuck on a grid of your own?
Type the position into the solver and it walks the whole solution, naming the technique behind every step — including this one.
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