This site is a set of static files. There is no account to create and no server that receives what you do in a puzzle.
Your settings, your progress on a grid, and your best times are kept in your own browser's local storage. They stay on the device you played on. Clearing your browser data removes them, and nothing here can read them back.
Anonymous usage measurement records which pages were opened. It does not record the puzzle you were solving, how long it took, or anything you typed. It can be blocked with any standard content blocker without breaking the site.
Advertising is served by Google AdSense, which may set cookies and use them to show ads. Google explains what it collects and how to opt out at policies.google.com/technologies/ads.
No personal data is sold, and none is shared with anyone beyond the advertising described above.