Chart Drill has no accounts and asks for nothing about you. Your progress stays in your browser. With your permission, and only then, it sends anonymous usage statistics to an analytics service so the lessons can be improved. No ads, and nothing is sold or shared for marketing.

The app saves the following in your browser’s local storage. It never leaves your device and you can wipe it at any time from Settings or by clearing site data:

• which lessons you have completed, your best scores, and your day streak;
• a lesson you are partway through, so a page reload can resume it;
• your analytics choice (allowed or declined).

On your first visit the app asks whether it may collect anonymous usage statistics. If you say yes, it sends these events to PostHog, a product-analytics service that processes them on our behalf:

• a lesson was started, resumed, finished, or quit, and at which question;
• whether an answer was right or wrong, and whether it was a redo;
• whether a result was shared, and taps on the feedback link;
• a page view, the page path, your browser type, and screen size.

Events are tied to a random identifier stored in your browser, not to a name, email, or account, because the app has none of those. Autocapture and session recording are switched off, no cookies are set, and browser “Do Not Track” is respected. As with any web request, PostHog receives your IP address to deliver the request and may derive an approximate location from it. We do not try to identify you from any of this.

Changing your mind: switch analytics off or on in Settings. Switching off stops all events and discards the random identifier.

• Hosting. The site is served by Vercel, which keeps standard server logs (such as IP address and request time) for security and operations.
• Feedback. The feedback link opens a Google Form. Anything you type there is handled under Google’s privacy policy, and you choose what to include.

Depending on where you live (for example the EU/UK under GDPR, or California under the CCPA/CPRA) you may have rights to access, correct, delete, or restrict the use of your personal data, and to object to processing. Because Chart Drill holds no account or contact details, the practical steps are:

• progress and settings: clear them in Settings or by clearing site data;
• analytics: switch it off in Settings, which discards the identifier;
• anything else: send a request through the feedback form. We will respond within 30 days.

We do not sell personal data and do not share it for cross-context advertising.

Chart Drill is not directed at children under 16 and does not knowingly collect personal data from them.

If this policy changes, the date at the top changes with it. Material changes will be noted in the app.