Free public beta until December 4, 2026:
every course is open, no card needed.
After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept.
How the beta works
generic trait
A trait with a type parameter, so a type can implement it several times.
A generic trait (trait From) can be implemented once per type argument, so one type may implement From and From.