good catch. it should be fixed now for users that have those settings turned on. much appreciated!
I didn't even know I had prefers-reduced-motion turned on and I certainly didn't know it affected web pages via CSS!!!
Another 0/1 bit for fingerprinting. Doesn't appear in https://coveryourtracks.eff.org/ (panopticlick). Also see prefers-contrast, prefers-reduced-transparency, prefers-color-scheme, inverted-colors
Please revert the "fix" that makes it so your demo is not seen at all.