Neon Nine Grid Sudoku | One Solution, and Hints That Explain Why
Fill the 9×9 grid with the numbers 1 to 9. Each puzzle is built on the spot and only appears if it has exactly one solution. When you get stuck, the hint button gives the next cell and explains in words why that number goes there.
💡 About This Tool
The level depends on the reasoning a puzzle needs. After building a puzzle, the game solves it using the simplest techniques first, and the hardest technique it had to use sets the level.
| Level | What it takes | Minimum givens |
|---|---|---|
| Easy | Only spot, last number | 36 |
| Medium | Line squeeze, box lock, two cells with two numbers | 27 |
| Hard | Three cells with three numbers, four corners, three-way fork | 22 |
| Expert | The techniques above run out, so you must try a number | 17 |
Now and then a puzzle misses its target level. When that happens, the rating appears next to the puzzle number.
Your record time is the time taken plus 30 seconds per hint. Viewing the same hint again on an unchanged board adds nothing. Your rank comes from the record time.
| Level | S | A | B |
|---|---|---|---|
| Easy | 4 min | 7 min | 12 min |
| Medium | 7 min | 12 min | 20 min |
| Hard | 12 min | 20 min | 35 min |
| Expert | 20 min | 35 min | 60 min |
Anything slower is C. Numbers placed that differ from the answer count as mistakes on the result screen, but they don't affect the rank.
🧐 FAQ
Q: Can I play with a keyboard? A: Yes. Arrow keys or WASD move, and 1 to 9 enter numbers. Shift plus a number writes a note, N switches note mode, 0 or Delete erases, Ctrl+Z undoes, Ctrl+Y redoes, H gives a hint and P pauses.
Q: What happens if I close the page mid-game? A: Next time you can continue, with the board, notes, time and undo history as you left them.
Q: What is today's puzzle? A: A puzzle built from the date, so it is the same for everyone on the same date. The weekday sets the level: Monday is Easy; Tuesday, Wednesday and Friday are Medium; Thursday and Sunday are Hard; Saturday is Expert. Only your first solve of the day counts. The day changes by your device's clock.
Q: When does the timer stop? A: When you press pause, switch to another tab, or scroll until the board leaves the screen. The board stays hidden while the timer is stopped.
Q: Do hints read my notes? A: No. They use only the numbers placed on the board. If a placed number differs from the answer, the hint points to that cell first.
📚 Fun Facts
The puzzle is generally credited to Howard Garns, a retired architect from Indiana. Dell Magazines first printed it in 1979 under the name Number Place.
It reached British newspapers much later. Wayne Gould, a retired judge from New Zealand, found it in a Tokyo bookstore in 1997 and spent years writing a program to generate puzzles. The Times started printing them on November 12, 2004, under the spelling Su Doku.