Notes on this puzzle
28 digits are printed in this grid and the other 53 cells are yours to fill. A solver that never guesses gets through it in 56 steps.
Most cells fall to the hidden single move: 49 of the 56 steps. Single candidate accounts for 4 more. The toughest moment needs pointing pair, and that single step is what sets the level.
Among the givens, 7 is the most common digit (6 times) and 8 the rarest (1). The emptiest box is the top-middle one, with 2 givens; the top-left box is the most crowded, with 5.
Where to beginLook at row 3, column 7 first: a hidden single is available there from the very start. Pencil in candidates for one box at a time and watch for two cells that share the same pair.