Write, run and be judged in the browser
Python, Java and C++ against hidden test cases, with a step-through view that shows a student exactly where their logic went wrong.
- Hidden and visible test cases, with the failing input shown after a genuine attempt
- Recorded step-through of a run — variables changing, line by line
- Logic → Code teaches the reasoning first, then fades the scaffolding away
- Unsubmitted work is kept per language, so a refresh never loses an attempt
The detail that makes it checkable
Every run is a real execution, not a pattern match against an expected answer.
Free to learn · paid to be measured
Read the courses for nothing. Pay when you want to be marked.
Every lesson on this site is free and needs no account. What a subscription buys is the graded practice, the full-length mocks, the spoken AI interviews and a readiness score you can act on.