Hard things, drawn simply.
Everything a CS degree teaches, explained like you’re 5.
Visual, hands-on computer science for smart people who were taught badly. From bits to distributed systems, one small, colorful step at a time.
No account. No credit card. Your progress stays in your browser.
Which sounds like you?
Every lesson, six small steps
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1. Story
An everyday analogy, like a coat check or a phone book.
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2. Play
Poke, drag and flip things until the idea clicks.
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3. Name it
The real terms, translated into plain English.
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4. Build it
Write real code right in your browser.
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5. Challenge
A harder twist, with hints if you want them.
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6. Remember it
Collect concept cards that bring the idea back later.
Stuck? Every big idea has an 🔄 Explain it another way button. Mistakes cost nothing.
Color in computer science
The whole curriculum is a map. Finish a course and its town fills with color.
Foundations · free
Level 0Hello, Computer
0/4 colored inLevel 1Math Toolbox
0/5 colored inFree where it matters most
Foundations
Free
43 courses covering everything taught in a bachelor’s-level CS program: programming, math, data structures, algorithms, systems, AI and more. Every lesson, project and exam.
Advanced ⭐
$5/month
29 master’s-level courses: distributed systems, deep learning, LLMs, security, theory and more. Coming soon; the first lesson of each course will be free.
The curriculum was built by studying the core CS programs of the world’s top-ranked computer science schools and the ACM/IEEE CS2023 curriculum guidelines. How we built it.