Free to learn. Pro is not on sale yet.
Every lesson is free, on the web and in both apps, with no account needed. Pro adds practice on top.
Free
- Every lesson and visualization
All topics, categories and tracks, stepped through one decision at a time.
- Predict mode
The player freezes before each decision and asks what happens next.
- Tracks and saved progress
An ordered path through the curriculum, remembered across visits. No account needed to learn.
- Run your own code
Write Python or JavaScript and run it against the lesson's examples, in your browser.
Pro
- Readiness score
A score per topic from your prediction accuracy.
- Review queue
Everything you predicted wrong, resurfaced until it isn't.
- Timed drills
The same lessons, against a clock.
In the apps
Bought in the iOS or Android app, Pro goes through the App Store or Google Play at the price they set. It unlocks on your account, wherever you bought it.
Refunds
Within 14 days, no questions asked. App Store and Google Play purchases are refunded by Apple or Google. Refund policy
Questions? See Help, or contact us.