tiagovtristao/jsplaygrounddev ? reverse-engineered prompt

Build me a simple web based JavaScript playground with instant feedback, something people can open in the browser and quickly try out small ideas without any backend or server side magic.

I want a clean, fast, no fuss experience where I can type code, see the result right away, and easily prototype JavaScript and other basic web stuff like HTML and CSS. Keep it elegant and lightweight, with a focus on speed and simplicity over lots of extra features.

Please make it work as a static site only, so it should not depend on any server dynamism or complicated setup. If you need to check the latest docs for anything, go ahead and look them up. The main goal is to feel polished and useful for quick experimentation, with immediate feedback as I edit.