Select a cell, then tap a number to fill it in.
Sign in to save your result to the global leaderboard.
Hard puzzles ask you to stay patient when ordinary scanning stops. Treat candidate notes as a map: one coherent pattern can remove possibilities and reopen the grid.
Hard Sudoku · patterns with purpose
Turn candidate structure into progress
Hard puzzles ask you to stay patient when ordinary scanning stops. Treat candidate notes as a map: one coherent pattern can remove possibilities and reopen the grid.
A useful routine for hard puzzles
- 1Refresh simple scans after every elimination; an advanced step often creates a new single.
- 2Keep candidates complete enough to compare the same digit across rows and columns.
- 3Look for a precise pattern, apply only its proven elimination, then return to the basics.
Best for
You are comfortable working from candidate notes.
You will practise
Proven eliminations and patterns such as X-Wing.
Move on when
You solve hard grids with patterns instead of guesses.
Why Sudoku Luna?
- Four difficulty levels from easy to expert
- Daily challenge with a global leaderboard
- Smart hints that teach real solving techniques
- Notes, undo/redo and automatic error checking
- Dark and light mode with an elegant design
- Print puzzles as PDF in multiple layouts
Frequently asked questions
Are hard Sudoku puzzles solved with trial and error?
No. The intended route is logical. Advanced patterns reduce candidates, then simpler moves usually become visible again.
When should I use candidate notes?
Use them as soon as direct placements run out. Accurate candidates are the evidence behind pair, intersection and fish patterns.
Why do simple moves return after an elimination?
Every proven elimination changes the candidate map. A cell that was ambiguous can become a single, so a return scan is always worthwhile.
Do I need to know every advanced technique?
No. Do not hunt for every shape at random. Start with one clear family, such as pairs, intersections or fish, and follow only a proven pattern.
When is expert Sudoku a good next step?
Move on once you maintain candidates cleanly and solve hard puzzles reliably with patterns rather than guesses.