👋 New to Kotlin? Start here.
Follow this path in order — each step builds on the last.
Your learning path
📑 Reference Pages
Deep dives into each part of Kotlin. Read when you need to understand something properly, or use as a lookup while coding.
Kotlin Overview
Null safety, JVM interop, the Kotlin ecosystem.
Null Safety & Types
?, !!, let, also, run — Kotlin's null system.
Idioms & Stdlib
Data classes, extension functions, apply, stdlib essentials.
Coroutines & Flow
suspend, launch, async, Flow for reactive streams.
▶ Run Code & Copy Snippets
Copy ready-to-use code patterns or run Kotlin right in your browser.
🛠 Projects
60 projects available in Python — Kotlin versions planned. Same project topics, same walkthrough structure.
🟩 Foundations
Short programs using basic syntax only.
Number Guessing Game
To-Do List
📊 Go Further
Compare Kotlin to Other Languages
Side-by-side syntax comparison across all 11 languages on The Codex.
History of Programming Languages
How Kotlin came to be, what problems it solved, and how it fits the bigger picture.
Programming Glossary
Plain English definitions for 80 terms — variable, function, loop, class, API, and more.