Play icons in YouTube, Spotify and Apple Music are not mathematically centered – they are optically centered. Most icon systems adjust this manually.

I'm collecting perceptual data to explore whether a CSS “optical-center” property could be defined, similar to how fonts have baseline metrics.

The experiment takes about 5–7 minutes (40 steps) and works on mobile and desktop. No login required.

Results and the dataset will be shared publicly after collection.

https://harley-sponsored-toolbox-operation.trycloudflare.com