GlenDoku — Sudoku Strategy Guide
GlenDoku is a clean sudoku with multiple difficulty levels. If you have ever stared at a grid unsure where to start, this guide gives you a repeatable method — from the first empty cell to the final 9. No guessing required.
The rules in ten seconds
Fill the 9×9 grid so every row, every column, and every 3×3 box contains the digits 1–9 exactly once. That single rule is all you need; everything else is technique.
Technique 1 — Scanning
Scan rows, columns and boxes for a digit that already appears often; the missing spots for that digit get constrained quickly. Start each puzzle by noting which numbers are already placed.
Technique 2 — Cross-hatching
Pick a digit and look at one box. Which of its nine cells can still legally hold that digit? Eliminate cells shared with a row or column that already contains it. Often only one cell remains.
Technique 3 — Naked singles
When a cell's row, column and box already contain eight different digits, the ninth is forced. Naked singles are the backbone of easy and medium puzzles.
Technique 4 — Hidden pairs
Sometimes two cells in a unit can only hold the same two digits. Those digits can then be removed as candidates from every other cell in that unit — a powerful way to break tough grids.
Beginner tips
- Use the notes/memo helper to track candidates.
- Solve the easiest naked singles first to open up the grid.
- Switch to a harder level only after medium feels comfortable.
Mistakes to avoid
Don't guess when two candidates remain — step back and look for a hidden pair. And don't forget the 3×3 boxes; players fixate on rows and columns and miss box constraints.