Get help, send us an idea, or see what changed in each release.
On the sign-in screen, tap "Forgot Password". We send a sign-in link to your email. Tap the link and you are in.
Yes, the free plan gives you the daily questions, the primer, and the feed. The Pro plan adds the System Design Lab, custom practice sets, and more. Pro is sold in the iPhone app.
Answer one question and your streak goes up by one. Miss a day and it goes back to zero. We always keep your best streak.
Not yet. SD Primer needs an internet connection. Offline mode is on our list.
Questions you got wrong come back first. Then you get new questions. Then extra practice. A question you get right comes back less often.
Open the Feedback tab above and email us. Tell us what you did and what you saw.
It is free. You do not need an account. Also on iPhone.