Generated debugging exercises with feedback that explains

Generated bug-hunting exercises

Challenges present code that compiles or runs but behaves incorrectly. The defect is the point: you find it, explain it, and fix it.

• Nine languages, from JavaScript and Python to SQL and C++.
• Curated public challenges you can repeat as many times as you like.
• A free generated challenge each day, without a subscription.

Feedback that names the cause

After you submit, feedback focuses on the underlying cause and whether your change resolves it. The evaluator checks whether the fix holds, including the case where a change looks right but leaves the bug in place.

Guided hints when you are stuck

Each challenge can surface a short, escalating hint so you keep momentum without being handed the answer. Hints point at where to look before they narrow to what to change.

Difficulty that adapts to you

Difficulty moves with your results so challenges stay useful rather than trivial or overwhelming. Progress is directional: it reflects the practice you have done, not a promise about performance elsewhere.

Related pages