I’m looking to turn my rupture-disc sizing spreadsheet into a secure, responsive web application. The site will sit behind a straightforward username/password gate; once signed in, users should be able to enter process parameters, hit “Calculate,” and instantly receive accurate sizing data. Those results must be downloadable as both polished PDFs and clean Excel workbooks. Security matters almost as much as accuracy. I run regular security audits, so the code needs to be structured for easy penetration testing, and every login or calculation must be written to an activity log I can review or export later. Think clear separation of concerns, meaningful commit history, and no hard-coded secrets. Specific deliverables • Full-stack application with basic credential login • Validated input form, high-precision calculation engine, and instant PDF / XLSX export • Activity-logging layer capturing user, timestamp, and input set for each run • Admin endpoint or simple UI to pull logs for audit purposes • Deployment guide (Docker, Heroku, or similar) plus thoroughly commented source in Git Acceptance criteria Results must replicate my reference outputs within ±0.1 %, exports must follow the layout I provide, and the audit log must prove every calculation can be traced back to a unique user action. If you’re comfortable translating engineering formulas into clean, test-covered code, and you can demo a working prototype on your own host before hand-off, let’s get started. You can take reference of similar site from: https://zookdisk.com/z-size/