Notes on this puzzle
30 digits are printed in this grid and the other 51 cells are yours to fill. A solver that never guesses gets through it in 58 steps.
Most cells fall to the hidden single move: 49 of the 58 steps. Pointing pair accounts for 6 more. The toughest moment needs XY-Wing, and that single step is what sets the level.
Among the givens, 4 is the most common digit (5 times) and 3 the rarest (2). The emptiest box is the top-middle one, with 2 givens; the top-right box is the most crowded, with 4.
Where to beginLook at row 2, column 9 first: a hidden single is available there from the very start. Expect a stage where only a pattern across several lines moves the grid on; full notes make it visible.