To get sudoku 129 better, you must master three intermediate techniques. Beginners rely on "sole candidate" and "unique candidate." For puzzle 129, that is just the warm-up.
Most beginners treat Sudoku as a game of trial and error. The “better” way is to treat it as a logic grid optimization problem. The 129 method forces you to: sudoku 129 better
Once candidates are reduced to one possibility, place it immediately. Better solvers don’t hesitate. They also chain placements: placing a number often creates another hidden single elsewhere. To get sudoku 129 better , you must
When you have a candidate number (say, a '5') that only appears twice in two different rows, and those twos line up in the same two columns, you have an X-Wing. This allows you to eliminate that '5' from all other cells in those columns. The “better” way is to treat it as
Pro tip: Puzzle 129 almost always contains an X-Wing in the middle phase (rows 4-6, columns 4-6). Search for it aggressively.