Privacy Policy
Prof. Sema · Last updated: 2026-06-07
What this is
Prof. Sema is a free interactive study tool for OS concurrency concepts, operated by Einar Yang (einar.top). This page explains exactly what data the app handles and why. The whole app works without an account.
What We Collect
Anonymous usage events: which levels are opened, which operations are picked (correct or trap), deadlocks, completions, undo/reset, language changes — carrying only a random anonymous id generated on your device, no name, email, or IP stored by us. If you sign in: your email, display name, sign-in provider (Google or Apple), and your level progress, so it can follow you across devices. We do not collect passwords (sign-in happens on Google/Apple), payment data, contacts, or anything else from your device.
Where It Lives
All data is stored in Cloudflare D1 behind api.einar.top. Web sessions use httpOnly signed cookies; the iOS app stores its session and local progress in on-device Preferences. Web progress and preferences live in your browser's localStorage, which you can clear at any time.
What We Never Do
No selling of data, no advertising, no third-party analytics SDKs, no cross-site tracking. Usage events exist solely to improve how the app teaches.
Deleting Your Data
Signed in? Account → Delete account permanently removes your user record, sessions, and synced progress in one click. Anonymous usage events are not linked to the deleted account identity.
Children's Privacy
Prof. Sema is an Education-category tool aimed at post-secondary students and does not knowingly collect personal data from children under 13.
Contact
Questions or requests (export, correction, deletion): einaryangca@icloud.com. We comply with PIPEDA (Canada) and the GDPR. This page mirrors the in-app privacy policy at einar.top/prof-sema#/privacy.