The tools
Every one of these is in the app today. Where a limit applies it is written down here rather than discovered later.
Code Lab
A real editor in a browser tab: a file tree, tabs, a split preview and a console. JavaScript, HTML, CSS, Markdown and JSON run on the page itself and Python runs as WebAssembly, so nothing leaves your machine; C, C++, C#, Java, Go, Rust, TypeScript, PHP, Ruby and Bash compile on a sandboxed runner.
AI study assistant
Ask about the thing you are actually studying. It answers from the course or document in front of you, writes practice quizzes from it, and reviews the code you wrote in the Lab.
Chat about the current lesson
Quizzes generated from it
Line-by-line code review
443+
A curated catalog
Courses, documentation sets and video libraries across 16 subjects, filtered by difficulty and kept to sources worth your time. Browse the catalog.
Summaries of your own material
Upload a PDF or a Word document — lecture notes, a spec, a textbook chapter — or point it at a video, and get a structured summary you can then ask questions about. The parsing happens in your browser; the free tier includes three summaries a day.
DOCX
Video
Daily Solve
One problem a day, opened in the Lab, with the assistant there when you are stuck. It is the shortest thing on this page and the reason people come back.
Progress that is actually recorded
XP for finished lessons, quizzes passed and problems solved; a streak that counts the days you showed up; badges for the milestones. Your courses, and where you stopped in each, are on the dashboard.
XP
Per lesson,
quiz and solve
11
Badges
to collect
Also in the app
Smaller things that turn out to matter once you are in here every day.
Documentation library
The reference material — MDN, language docs, standards — kept next to the courses instead of in a browser bookmark folder.
Video library and search
Search YouTube from inside the app and watch without a sidebar of recommendations trying to move you along.
My courses
What you started, what you finished, and what you abandoned in week two. Progress is tracked per lesson, not per course.
Light and dark
Both themes, everywhere, remembered — and every animation stops if your system asks for reduced motion.
Try it before you pay for it
The free tier searches the whole catalog, tracks your progress and includes Daily Solve. No card, no trial clock.