Privacy
In short
There are no accounts, nothing personal is stored on a server, and there are no ads. Your progress and your records live in your own browser.
What is kept in your browser
The puzzle in progress, your settings and your personal records are stored in your browser's localStorage. None of it leaves your device, and nobody — the site's operator included — can read it.
- The puzzle in progress — the board, the digits you entered, your candidate marks, elapsed time, and the cells the answer check found wrong
- Settings — language is not among them, because each language has its own address
- Personal records — best time and completion count per difficulty
- Your best Rush score and combo
- Practice attempts and completions per technique
Clearing site data in your browser removes all of it at any time. The puzzle in progress and your records go with it, and there is no way to get them back.
Cookies
This site sets no cookies. Unlike a cookie, localStorage is never attached to a request and sent to a server.
What is sent to a server
Building a new puzzle sends a request to the puzzle API. It carries the number of clues you asked for and nothing else — no progress, no records. The server builds a puzzle, returns it, and keeps nothing.
Like any web request it passes through the hosting provider's infrastructure (Cloudflare), which may process access logs for its own operations and security. That is not data the site's operator controls or reads.
Analytics and advertising
There is no analytics, no tracking script and no advertising on this site today. This page will be updated before any of that changes.
Share links
Sharing puts the board and your entries in the fragment of a link — the part after the #. A fragment is never sent to a server, but anyone you give the link to can read it. Sharing only ever happens when you ask for it.
Contact
Questions about any of this can go to the address below.