The biggest open learning codebase on Earth. Beyond studying from it free online, downloading it shows how a massive learning platform is engineered — curriculum as code, testable challenges, and progress tracking at planetary scale.
Why download it: pair it with Producators courses for extra practice, and study its challenge/test design to understand how coding skills get verified automatically.
Get started: follow the contributing docs to run it locally, or simply learn free on the site. BSD-3-Clause licensed.