Learn to code like it's a game

Pick a course, follow its trail

Every course is a map of units: finish a lesson and the next one opens. Start with any course; the first two units are free.

Learn by doing: build real projects

A project is one complete app, built step by step. Every step adds a feature to your own code and is tested in your browser, and at the end the finished app is yours to run and share. The first two milestones are free.

• APP

  Build a Task Manager App in React

  A task manager that adds, finishes, edits, filters and deletes tasks, remembers them and loads them from an API.

  Milestones

  6

  Steps

  21

  Free steps

  8

  Free: milestones 1 and 2 (8 steps).Free: milestones 1–2

  Start buildingStart See the stepsSteps
• WEB

  Build a Portfolio Site with HTML & CSS

  A one-page portfolio site with a hero, project cards, an About section and a contact form, responsive and keyboard friendly.

  Milestones

  4

  Steps

  13

  Free steps

  6

  Free: milestones 1 and 2 (6 steps).Free: milestones 1–2

  Start buildingStart See the stepsSteps

Not sure where to start? Follow a roadmap

A roadmap puts courses in the order that builds on itself, so you always know what to learn next. Steps whose course is still being written show as coming soon.

• Frontend Developer roadmap

  From your first HTML page to building apps with React, in the order that builds on itself.

  1. </> Step 1: HTML Mastery
  2. CSS Step 2: CSS Mastery
  3. WEB Step 3, optional: Build a Portfolio Site with HTML & CSS
  4. JS Step 4: JS Mastery
  5. API Step 5: Web APIs and Browser Internals
  6. TS Step 6: TypeScript Mastery
  7. JSX Step 7: React Mastery
  8. APP Step 8, optional: Build a Task Manager App in React

  8 steps 6 courses ready, 2 projects

• Interview Prep roadmap

  JavaScript fluency, the data structures and patterns coding interviews test, then frontend system design.

  1. JS Step 1: JS Mastery
  2. API Step 2: Web APIs and Browser Internals
  3. { } Step 3: DSA Mastery
  4. SD Step 4: Frontend System Design

  4 steps 4 courses ready

• Backend Developer roadmap

  JavaScript on the server: APIs, databases, authentication and shipping real services.

  1. JS Step 1: JS Mastery
  2. NODE Step 2: Node.js Mastery
  3. API Step 3: REST APIs with Express
  4. SQL Step 4: SQL and PostgreSQL
  5. DB Step 5: MongoDB
  6. AUTH Step 6: Auth and API Security
  7. SD Step 7: Backend System Design
  8. OPS Step 8: Docker, CI/CD and Deployment

  8 steps 8 courses ready

Try it in the playground

Free online editors for quick experiments: run JavaScript and TypeScript, build a React component or a web page, and share it with a link. No sign-up needed.

• JS Online JavaScript compilerRun JavaScript and see the console output, with the line of every error.
• TS Online TypeScript compilerRun TypeScript with real type checking: type errors are underlined as you type.
• </> Online React compilerWrite a React component in JSX or TSX and use it in a live preview.
• <#> Online HTML CSS editorBuild a web page in index.html, style.css and script.js with a live preview.

Every lesson in four steps

Read and run, watch it move, check yourself, then write the code.

1. Learn and run

   Short explanations with examples you run and edit in place.

   const doubled = [1, 2, 3].map((x) => x * 2);
   console.log(doubled);

   Run[2, 4, 6]

2. Visualize

   Step through the algorithm, frame by frame, on its own inputs or yours.

3. Quiz

   Quick questions with instant feedback. Pass to earn the lesson's second star.

   AO(n²) O(n log n) CO(1)

4. Solve

   Real coding problems, tested in your browser the moment you press Run tests.

   empty listone itemduplicateslarge input 4 of 4 tests pass

Every step earns something

XP for every read, run, answer and solve. Levels, streaks and badges keep you coming back.

Start free. Go Pro when you are ready.

Questions