Rameshpd2748/Real-life-sudoku-puzzle ? reverse-engineered prompt

Build me a simple browser based Sudoku app that feels like a real puzzle I can use on one page. I want a clean 9 by 9 grid where I can type numbers, see the board clearly, and click a button to solve the puzzle using a backtracking approach. It should stop me from putting in obviously invalid values, and if the puzzle cannot be solved it should tell me in a friendly way instead of just failing silently.

Please make the page look neat and modern with basic responsive styling so it works nicely on a laptop or phone. Keep it lightweight with plain HTML, CSS, a little Bootstrap style if it helps, and vanilla JavaScript. I would also like simple controls like solve, clear, and reset so it is easy to try different puzzles. Keep the code readable since I may want to learn from it later. If you need to, look up current Sudoku solving examples online for reference.