Rasik1407S/Python-Micro-Project ? reverse-engineered prompt

Build me a simple Sudoku game that runs with a Python backend and a single HTML front end, with no build step and no local frontend setup. I want the Python side to generate valid Sudoku puzzles, make sure each puzzle has one solution, check moves as I play, give me hints, and let me auto solve the board if I want. The browser should just render the grid, let me click or use the keyboard to fill numbers, highlight mistakes right away, and show a timer while I am playing.

Please make it feel polished and dark themed, with a clear selected cell, original clues locked in place, and easy difficulty switching that starts a fresh puzzle. It should be okay to load React from a CDN in the HTML file, and use Flask for the API. If you need to check current docs or best practices, look them up online first.