Giri-Aayush/Plagiarism-Detector ? reverse-engineered prompt

Build me a simple web app that checks whether a piece of text looks plagiarized and shows a plagiarism percentage right on the page.

I want a clean, easy to use form where someone can paste text, submit it, and get an instant result. The app should compare the input against the sample text data in the project, normalize the text by making it lowercase and removing punctuation, then use TF IDF and cosine similarity to calculate how close the texts are. Please make the result easy to understand for students or teachers, with a clear percentage and a short explanation of what it means.

Use the existing Python and Flask setup, keep the interface straightforward, and make sure the whole thing runs locally without extra hassle. If anything is unclear, look up current docs online if you need to, but keep the build focused on this plagiarism checking workflow.