Offline HTML Calculator Adaptation

I have a small single-file HTML calculator that already performs my own custom formulas perfectly on my Mac. The problem is that the same file refuses to run on my iPad, and by extension on my iPhone. I need you to troubleshoot whatever is blocking it on iOS Safari, clean up the code if necessary, and package a self-contained version (all CSS, JS, fonts, and images inlined or locally referenced) so it works offline on Mac, iPad, and iPhone alike.

The workflow I’m picturing is simple: once you’re finished, I should be able to drop the .html file into Mail and send it as an attachment; the recipient opens it and the calculator just works—no server, no internet, no extra setup.

Key points you’ll cover:
• Preserve my existing custom-formula logic exactly as is, unless a tweak is required for cross-device compatibility.
• Remove or replace any calls that rely on external CDNs or modules that break offline use.
• Make sure touch events, viewport meta tags, and mobile Safari quirks are handled so buttons respond just as they do on desktop.
• Keep the file lightweight and readable so I can still edit formulas later myself.

When it’s done I’d like:
1. The final, fully functional offline .html file.
2. A short note (markdown or txt) explaining what you changed and, if relevant, where I’d edit to add new formulas in future.

If you have an iOS device to test on, let me know; otherwise we can do a quick test round together before sign-off.