Frequently Asked Questions

The most common questions about puzzles, hints, saving and the display.

Does every puzzle have exactly one solution?

Yes. After a puzzle is generated, a solver checks that it has exactly one solution and can be solved from start to finish using only the techniques in this guide. You will never get a puzzle that needs a guess or has two valid answers.

I am stuck. Do I have to guess?

No. Being stuck means there is a deduction you have not spotted yet. Try these in order:

1. Pick another number and scan every box again (hidden singles).
2. Press "Auto notes" and look for a cell with only one note.
3. Use the intermediate and advanced techniques to remove notes.
4. Press Hint: it tells you which technique comes next.

Do hints affect my records?

A game where you used hints still counts as a win, for your win rate and for your daily streak; it just does not count toward your best time. A hint that points out mistakes also counts as a hint. Auto notes do not.

Why does the hint ask me to erase mistakes first?

When there is a wrong number on the grid, every deduction after it goes wrong too, so the hint marks the wrong numbers in red first. This happens even when the mistake check is "Off", because a hint must reason from a correct grid.

Where is my progress saved? Can I continue on my phone?

Your game in progress, stats and settings are all saved in this browser, with no account needed. On another device, in another browser or in a private window, you start fresh; clearing the browser's site data also erases your records.

When does the daily challenge change?

At midnight in your time zone. The puzzle for a given date is the same worldwide, so you can race your friends on it. See Daily challenge.

Why did a number key fade?

All nine of that number are on the grid, so the key shows a check mark. If one of them is wrong, erase it and the key comes back. You can still use it in notes mode.

Where did the timer go?

"Hide the timer while playing" is turned on in the settings. The time is still recorded and shown when you finish.

Can I play offline?

Puzzles are generated in your browser, with no server involved. Once the game page has loaded, you can finish the current game even if your connection drops.

Is there a dark mode?

Yes. Choose light, dark or follow the system under "Theme" in the settings.