Question 1

How do I play?

Accepted Answer

Choose a difficulty → click an empty cell → enter a digit 1–9. If you're unsure, turn on Notes to record candidates in the cell. Use Hint when stuck. Your progress is auto-saved so you can continue next time.

Question 2

What's the goal of the game?

Accepted Answer

Fill the 9×9 grid with digits 1–9 so that each row, each column, and each 3×3 box contains all digits 1–9 exactly once, with no conflicts.

Question 3

Can digits repeat within a row, column, or 3×3 box?

Accepted Answer

No. Each row, column, and 3×3 box must contain the digits 1–9 without repetition.

Question 4

Can I change the given digits (clues)?

Accepted Answer

No. Given digits are fixed and cannot be edited.

Question 5

How does Conflict Detection work?

Accepted Answer

If Conflict Detection is enabled, any invalid placement (like a duplicate in a row/column/box) is highlighted in real time so you can correct it.

Question 6

What difficulty levels and puzzle count are available?

Accepted Answer

About 3000 puzzles across five difficulty levels, suitable for beginners through experts.

Question 7

How do I enter or delete numbers?

Accepted Answer

Select a cell and press 1–9 on your keyboard to enter a digit. Press Backspace to delete. You can also tap/click the on-screen number buttons.

Question 8

How do Notes (candidates) work?

Accepted Answer

Click or press N to toggle Notes mode. Smart Notes can auto-generate and manage candidates, making logical solving much faster.

Question 9

I'm stuck—what should I do?

Accepted Answer

Use Hint (shortcut H). Hints point you toward a legitimate next logical step without spoiling the whole puzzle.

Question 10

Can I undo/redo?

Accepted Answer

Yes—unlimited undo/redo with Cmd/Ctrl + Z / Y.

Question 11

Will my progress be saved?

Accepted Answer

Yes. The game auto-saves. If you close the page or switch devices and come back, you can continue your current board.

Question 12

How are conflicts/errors indicated?

Accepted Answer

With Conflict Detection enabled, conflicts are highlighted instantly (e.g., duplicate in a row). A digit counter/tracker also shows usage of digits 1–9.

Question 13

Is it mobile/tablet friendly?

Accepted Answer

Yes. The UI is responsive and optimized for touch, with comfortable tap targets on phones and tablets.

Question 14

Can I create custom puzzles?

Accepted Answer

Yes. You can start from an empty grid and enter a custom puzzle, with validity checks to prevent impossible or obviously conflicting boards.

Question 15

Are there keyboard shortcuts?

Accepted Answer

Common desktop shortcuts:
• Arrow keys: move cursor
• 1–9: place digit
• Backspace: delete
• Esc: pause/resume
• H: hint
• N: toggle Notes
• Cmd/Ctrl + Z / Y: undo / redo

Question 16

Could I lose my progress?

Accepted Answer

Generally no—progress is auto-saved. Clearing your browser's site data may remove local saves, so do that with care.

Question 17

How is puzzle quality?

Accepted Answer

The built-in set is pre-generated and graded for stable quality. Custom puzzles also pass validity checks to reduce no-solution or trivial-conflict cases.

Question 18

Privacy & open-source license?

Accepted Answer

This game is based on the open-source project Super Sudoku under the MIT License. If you fork or self-host, please follow the MIT terms.

Question 19

The page won't load or keys don't work—what can I try?

Accepted Answer

Refresh the page or use a modern browser (Chrome/Edge/Firefox/Safari). On mobile, if your input method interferes, switch to a numeric keyboard layout.

Question 20

How do I reset the current board?

Accepted Answer

Use Clear/Reset to start over. If you want to keep your current progress and begin a new game, open a new tab or export first (depending on your site's implementation).

Question 21

Why do numbers have different colors?

Accepted Answer

Colors help you understand the game state:
• Black/White: Given clues (cannot be changed)
• Teal/Cyan: Numbers you filled in
• Yellow/Amber: When you select a cell with a number, all other cells with the same number are highlighted in yellow to help you see the distribution
• Red: Conflicting or incorrect numbers (if conflict detection is enabled)

Question 22

Why do some cells have gray backgrounds?

Accepted Answer

When you select a cell, the game highlights:
• Light gray: All cells in the same row, column, and 3×3 box as your selected cell
• Darker gray: All cells containing the same number as your selected cell
This helps you quickly identify conflicts and analyze the puzzle logic.

Question 23

How does Undo/Redo work exactly?

Accepted Answer

Undo (Ctrl/Cmd+Z) takes you back to your previous action. Redo (Ctrl/Cmd+Y) moves forward if you've undone actions. Important: If you undo and then make a new move, the 'future' history is discarded—just like most text editors.

Question 24

Why is the Hint button sometimes disabled?

Accepted Answer

The Hint button is only available when:
• You have selected a cell (click on an empty or user-filled cell)
• The selected cell is NOT a given clue (black/white numbers)

Hints only work on cells you can edit. If you select a given clue or haven't selected any cell, the Hint button will be disabled.

Question 25

What do the different settings options do?

Accepted Answer

• Show auto generated notes: Automatically displays all possible candidate numbers in empty cells, updated in real-time based on the current board state. Helpful for beginners to see available options.

• Highlight wrong entries: Marks any number that doesn't match the final solution, helping you catch mistakes early without waiting until the end.

• Highlight conflicts: Highlights duplicate numbers in the same row, column, or 3×3 box—basic Sudoku rule validation to prevent obvious violations.

• Show circle menu when a cell is clicked (desktop only): Shows a visual circular number picker when you click a cell on desktop, providing an alternative to keyboard input.

• Show occurrences of numbers in number buttons: Displays how many times each digit (1-9) has been placed on the board, helping you track which numbers still need to be filled in.

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