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Remote Ready Biology Learning Activities has 50 remote-ready activities, which work for either your classroom or remote teaching.
Ballerina Optical Illusion
Here's the illusion I mentioned in class... Get a bunch of people in the room and poll to see in which direction she's moving (I'd bet it's not the same for everyone!) Looking at her foot seemed to help me get her to switch and eventually you learn to get her to switch back and forth at will (very cool when you can keep her from doing a full revolution and just keep her switching back and forth three or four times...)
http://www.maniacworld.com/Spinning-Silhouette-Optical-Illusion.html