Prompt

Make a screen of 20 soft circles drifting around and bouncing off the edges. Make it a single HTML file that opens in a browser with nothing to install and no other files. Put the CSS and JavaScript inside it. Do not use image files or any external address; use emoji or letters if you need a symbol.

Each one has its own size, speed, and direction. They bounce off the walls and off each other, slowing slightly on each bounce and picking up again.

Colours shift slowly over time so the screen never looks the same twice.

Clicking adds one where I clicked. A slider changes how many there are.

Keep it smooth on a phone. If sixty is too many to run well, draw fewer rather than dropping frames.

When you are done, leave it running in your head for a few minutes and check nothing escapes the screen or piles up in a corner.