Biswas9999/spk ? reverse-engineered prompt

Build me a simple calculator web page in HTML that works in the browser.

I want a clean, easy to use calculator with buttons for numbers, basic operations, clear, delete, and equals. It should show the current input and the result clearly, and it should feel nice on both desktop and phone screens.

Please make it all work in one small project so I can open the page and use it right away. Keep the design neat and simple, with a modern look but nothing too fancy. If you can, make the buttons responsive and let people use the keyboard too.

If you need to check any current browser behavior or best practice, look up the latest docs online.