Coding courses and the sandbox

A language path is a curated route through a language: what to learn, in what order, with links to the source material for each step. Where a language has a full authored course, it goes further — a written curriculum of lessons grouped into modules, each with objectives, worked code, and exercises.

Lesson exercises run in a WebAssembly JavaScript sandbox in your browser. It has no network access and no access to the page, so code you write cannot reach anything, and nothing you write is sent anywhere to be marked. Your drafts and progress are stored locally.

• The scratchpad is the same sandbox with no lesson attached — for trying something out.
• X-ray a codebase reads source you provide and shows its structure: files, symbols, imports, and call sites. It is a reading tool, not a runner.

Each authored course has a citation index: the specifications and official documentation the lessons rest on, in one list. Use it when you want the primary source rather than the lesson's summary of it.