For mid-level developers

Think in systems. Ship with confidence.

You ship features reliably. Now learn to design the systems they run on. Interactive exercises that build architectural intuition through practice.

Start the System Design Course

From features to architecture

Learn to see how components connect. Each exercise builds your ability to reason about systems, not just endpoints.

SOLID principles at scale

Design principles apply to systems, not just classes. Learn how SOLID and DRY shape architectures that survive growth.

Scaling decisions you practice

Caching, load balancing, database sharding. Make these decisions in exercises before you make them in production.

System Design + SOLID + DRY

The technical depth that earns senior titles.

Try a Lesson

Write code from lesson one

Every lesson is an exercise you solve in your browser. Real code, real tests, real feedback.

Write a greeting function

main.ts

function greet(name: string) {

return `Hello, ${name}!`

}

Structured progression

Each concept builds on the last. You always know what to learn next.

Multiple exercise types

Quizzes, fill-in-the-blank, matching, and code keep every lesson engaging.

Instant feedback

Submit your answer and see test results in milliseconds.

Learn by doing

Solve exercises in your browser from the first lesson.

Try a Lesson

Join over 5,000 learners

Flutter Zero to Mastery

Explore our courses

Pick a course and solve your first exercise.

Dart Course

An interactive Dart course where you code, test, and build apps directly in your browser.

Try Course

Flutter Course

An interactive Flutter course where you code, test, and build apps directly in your browser.

Try Course

S.O.L.I.D. Course

Learn the principles of how software should be structured, so you can guide AI to build better systems.

Try Course

D.R.Y. Course

Learn to identify and eliminate code duplication, making your codebase cleaner and easier to maintain.

Try Course

System Design Course

Learn how APIs, databases, caching, and load balancing fit together to build scalable systems.

Try Course

Interactive courses

Every lesson is an exercise with instant feedback.

Get Started

Senior engineers think in systems. Start practicing.

Interactive exercises that build architectural reasoning.

Get Started