Interactive Primer — the tree of knowledge

Interactive Primer — free, open-source interactive lessons from the early years through K-12, university, and beyond

Free, open-source “smart web pages” that teach maths, compsci and physics from the age of 5 to 105. One tree of knowledge you climb at your own pace, with animations, interactive diagrams, and randomized quizzes. No sign-up, no subscriptions, no ads.

Courses

A guided path that threads many concepts into one coherent journey through a subject.

Concepts

A single bite-sized idea — a notion, definition, theorem, or technique — taught on one page.