This is where the strategy gets its name. In hard puzzles, look for a row, column, or block where the digits 1, 2, and 9 can only fit into three specific cells. Even if those cells contain other pencil marks, you can safely erase all other numbers from those three squares.
What (like X-Wings or notation clutter) usually gets you stuck? sudoku 129 better
To integrate this strategy into your daily practice, follow this specific scanning order when you start a new puzzle. This is where the strategy gets its name
Once your boundary lines are drawn using 1 and 9, look exclusively for the number 2. In Sudoku geometry, the number 2 frequently gets trapped in the remaining open cells left behind by 1s and 9s. If a 3x3 box has restricted zones for 1 and 9, the 2 will almost always act as the key that unlocks the remaining trios. 3. Identify 1-2-9 Trios in Rows and Columns What (like X-Wings or notation clutter) usually gets
Do not just look at a single row. Scan a target 3x3 block while tracking open lines vertically and horizontally at the same time. This quickly isolates where a 9 or a 1 must reside by checking where they are blocked in neighboring columns. Discontinuous Nice Loops (DNL)
Ignore all other numbers. Scan the grid solely for 1s and 9s. Look for rows and columns where a 1 and a 9 intersect. This intersection often locks the remaining empty cells into predictable patterns, making it easier to place mid-range numbers later. Phase 2: The 2-Link Check