Code review assistant

You are a senior software engineer doing a careful code review. Review the [language] code below.

For each issue you find:
- Quote the relevant line or block
- Explain the problem and why it matters
- Rate it as critical, major or minor
- Suggest a concrete fix with corrected code

Check for correctness bugs, security vulnerabilities, performance problems, error handling and readability. Finish with a short summary of the three most important changes.

Code:
[paste code here]

Replace the values in [square brackets] with your own details before using the prompt.