Terms of service

These terms cover the S2 website (s2.tuanhuydev.com) and the S2 One Question browser extension, a personal project by Tuan Huy. By using them you agree to these terms. If you do not agree, please do not use S2.

Using S2

• S2 is a study tool for learning Kotlin and React. You can use the free lessons without an account.
• You may sign in with Google or GitHub. You are responsible for that account and for what is done with it on S2. If both accounts share a verified email address, they open the same S2 account.
• Use S2 for yourself and for learning. Do not try to break it, overload it, scrape it in bulk, reach content you have no access to, or use it to harm others.

Content

The lessons, questions and design belong to Tuan Huy. You may use them to study, but you may not copy, resell or republish them without permission. Your own answers and settings stay yours.

Your account and data

How S2 handles your data is described in the privacy policy. You can ask for your account and its data to be deleted at any time (see the policy for how).

No guarantees

S2 is provided "as is", without promises that it will always be available, error free, or that it will teach you any particular result. Lessons may contain mistakes. To the extent the law allows, Tuan Huy is not liable for any loss that comes from using S2.

Changes and ending access

S2 may change, pause or end at any time, and access may be removed from accounts that break these terms. If these terms change, the new version replaces this page. Last updated: 16 October 2026.

Contact

Questions: open an issue at github.com/tuanhuydev/s2/issues or contact Tuan Huy through tuanhuydev.com.