Watch messy code get better, step by step.
Each lesson starts from working code with a real problem in it, then refactors it one small, safe step at a time until the idea is obvious. Step through it, stop on any change, and see exactly which lines moved and why.
DRY: one rule, one place ยท step 2 of 13
Working code
Every lesson starts from code that compiles and works, the way a reasonable developer would have written it.
The problem, circled
A change request arrives and hurts. The lesson names the problem and circles every line where it lives.
Small, safe moves
One named refactoring per step, and every step compiles. You watch tokens move instead of reading a wall of new code.
Before, after, and when
The start and the finish side by side, then when to reach for it and, honestly, when not to.
Lessons
Search by concept, by tag, or by what you're seeing in your own code.
No lesson covers that yet
Try a symptom instead of a name, like "a class that does everything", or clear the filters.