129: Sudoku

: In "Killer" variations of this volume, specific cell groups (cages) have fixed sums (e.g., a three-cell 24-cage must contain 7, 8, and 9). Thermometer/Arrow Constraints

While a standard Sudoku puzzle relies on placing digits 1 through 9 in rows, columns, and 3x3 grids, "129" often appears in more complex iterations: The Killer Sudoku 129 : Featured in The Guardian sudoku 129

Start with the number 1. Scan each row, column, and box. Place any obvious singles. Then move to 2, 3, up to 9. Repeat this cycle three times. : In "Killer" variations of this volume, specific