NNF pour like liquids but act like a solid when you put force on them. This means you can run across a pool of it, but you’ll sink into it like mud if you slow or stop.
Also, it reacts very neatly to the vibrations from a speaker.
It’s just corn starch and water. Ain’t science cool?
P.S. People who do not believe in evolution are not allowed to enjoy the fun science of these videos. :)