Each lesson is a small JavaScript kata. You write code in the editor and click Run Tests.
When all tests pass, click Complete Lesson to lock it in and move forward.
Your progress is saved to localStorage in your browser. Use Reset if you want a fresh start.
Safety note
Code is executed in a sandboxed iframe with a minimal API and a time limit. This is still a learning toy,
not a hardened security product—avoid pasting secrets.