I've just tried this in the latest Firefox 119 & Chromium 118 and the CodePen registers as 'idle' in the browser task manager and I can't see any difference in

I've just tried this in the latest Firefox 119 & Chromium 118 and the CodePen registers as 'idle' in the browser task manager and I can't see any difference in `top`. When it does register it's usually at ~0.001%. This isn't exactly a new machine either, wonder if it's falling back to CPU rendering in your configuration.