I added one more little “on-line experiment on #visualperception " to my collection
https://michaelbach.de/ot/cog-Ebbinghaus/index.html.
An #opticalillusion , over a century old, with animation to test yourself. Clearly the last one to add this year. And instead of adding new pages, I've been busy converting existing ones from Flash to Cappuccino (JavaScript) – a task nearly as arduous as creating from scratch.