About

Daily mental-arithmetic games, and a growing library of techniques you can practise rather than just read.

What it will never have

No accounts. No email capture. No ads, no affiliate links, no sponsored technique pages. No cookie banner, because there are no cookies to consent to. No streaks — a day off costs you nothing.

What it does with your data

Nothing leaves your browser. Which puzzles you've solved and how long you took are stored on the device you played on, and you can export or delete them at any time. There is no server to send them to.

For teachers

It's a URL you can put on a projector. Contrast is set for the back of the room, every control is at least 48px, and the technique pages work with JavaScript switched off — which some school devices do.

Corrections

If a puzzle looks wrong or a technique page has an error, that's worth knowing about — [email protected].