Debug. Visualize. Master.
The training platform that teaches what others skip — debugging real bugs, understanding how the browser actually renders your code, and building the skills that separate juniors from seniors.
Not another course platform
Everyone teaches you to write code. We teach you to understand, debug, and fix it.
Debug Real Bugs
Fix broken CSS, JS errors, React anti-patterns, and accessibility violations pulled from real-world code.
See How Browsers Work
Interactive visualizations of DOM tree building, CSS cascade, specificity, box model, and event loop — in real time.
Compete & Level Up
Race against the clock, earn XP, maintain your streak, and climb the leaderboard.
Live Sandbox
Full-featured code editor with instant preview and DOM tree visualization. Write code and see its internals.
Challenge categories
From CSS layout bugs to React performance anti-patterns. Every challenge mirrors a real production issue.
How it works
Read the bug report
Each challenge describes a real bug — broken layout, wrong behavior, accessibility violation, or performance issue.
Find & fix the issue
Use the built-in editor to locate the bug and write the fix. No writing from scratch — just surgical precision.
Learn the root cause
After solving, see the detailed explanation of why the bug happened and how the browser processes your fix.
Ready to see through the code?
Join developers who train the skill that matters most — understanding and fixing real code.
Start Your First Challenge