arm-x-Dev/SGPA-Calculator-VTU ? reverse-engineered prompt

Build me a single page VTU SGPA and CGPA calculator that feels modern, dark, and really polished, with a glassy look and smooth animations. I want students to be able to pick the ECE preset semester scheme or switch to a custom mode for any branch, then enter marks and credits and see SGPA update instantly as they type. Please also include a CGPA view that can combine multiple semesters using the usual credit weighted formula, and let users ignore subjects or unfinished semesters when needed.

Make it work well on mobile too, with a clean layout, easy typing, and a numeric keyboard for score fields. I also want a simple export option that generates a neat downloadable HTML report of the results, ready to print or save. Keep it fully offline and self contained, with no external dependencies, and make the whole thing feel premium and responsive across screen sizes.