About this project

What it is

Knowledge here is compositional. A concept is a short, self-contained page that answers “what is X?”. Each one pairs a written explanation with an interactive demo, then checks your understanding with a few questions. A lesson is a step in a course that composes concepts toward a goal. Every page is a named node, and the prerequisites between nodes are explicit edges in a shared graph.

It is free and needs no account. Your progress lives only in your own browser.

How it's built

• A typed registry is the source of truth. Concepts and lessons are entries in two data files with requires edges. A build step validates the whole graph and fails on any violation, so a broken reference or a dependency cycle cannot ship. The structure lives in the data itself.
• Static delivery, no server. The site is generated with Astro and served as plain static files on Cloudflare. Math is typeset at build time. There is no backend and no database; the only per-visitor state is progress in your browser's localStorage.
• A sandboxed widget platform. Each interactive is a self-contained widget. It runs in a sandboxed iframe with its own isolated origin, so it cannot reach the page around it. Widgets are versioned and embed with a single tag, and they share a small host protocol for theming and sizing.
• The build is the contract. All of it is checked automatically when the site builds, so a page that builds is structurally sound.

Contribute

This is open. The same contracts that keep the core honest apply to every contribution, so it is hard to break things by accident. You can write a new concept page, add a lesson to an existing course, or build an interactive widget.

Because the whole site is structured, AI agents do the mechanical work well. The repository ships Claude Code skills: /concept to author a page and /widget to build an interactive. They follow the rules and validate against the build. Describe what you want, and the agent scaffolds and writes it, then the build checks it.