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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

Learning that explains itself.

Every concept two ways — the rigorous version and the plain-English one — with something to play with every few paragraphs.

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Two explanations, always

The textbook treatment and a plain-English version, side by side.

Learn by doing

Drag the vertex. Rebuild the sentence. Answer a quick check every few paragraphs.

A tutor that asks first

Stuck? The AI tutor guides you with questions and hints — not spoilers.