Privacy
Short version: almost nothing leaves your device. No accounts, no ads, no tracking.
Stays on your device
Your work, settings, theme and language are saved in your browser's local storage. They never reach a server, and clearing site data removes them.
Share links
A share link holds your work inside the link itself. Nothing is uploaded; whoever has the link can open it.
Build with AI
Where an app offers it, the prompt you type is sent to Cloudflare Workers AI to generate a result. Prompts are not stored or linked to you.
Videos
Lesson videos play through YouTube's privacy-enhanced mode (youtube-nocookie.com), which sets no cookies until you press play.
Feedback
Messages you send come to me by email. Your email address is optional and only used to reply.
Donations
Payments are handled entirely by Stripe. Card details go straight to Stripe and never touch this site. See Stripe's privacy policy.
Hosting
The site runs on Cloudflare, which keeps standard short-lived request logs (such as IP address) for security. There are no ads and no tracking cookies.
Anonymous usage counts
To learn which tools help and which need work, the site counts visits without knowing who visited. Each count is a small message sent to this site (not to an ad or analytics company) with the page or simulation name, the country (coarse, never a city), whether the screen is a phone, tablet or desktop, light or dark theme, the website you came from (its name only), and the kind of button used in a simulation (for example the name of a mode button). It also counts how long a page stayed open in rounded buckets, and that a donation dialog was opened or finished, with the amount rounded to a range and one-time or monthly.
Not counted: anything you type, your searches, the questions you ask, your work, payment details, or your email. No cookies, no ids and nothing saved in your browser for this, so a count cannot be tied to you or followed from one visit to the next. Your IP address is not stored by us. Nothing is shared with other sites. If your browser sends Do Not Track or Global Privacy Control, nothing is counted at all.
Students and schools
Students never sign in or give personal information. The tools are safe to use in classrooms under COPPA and FERPA expectations because there is nothing to collect.
Questions? . Last updated October 2026.