Knight's tour animated with @geogebra. Thanks @mathforge & @baabbaash https://twitter.com/mathforge/status/1343700448985931776

Here's a thread of the making of the previous GIF. I used some new @geogebra tricks I'd like to share.
I started with a Polyline(A,B,C,D,E,F,G,H,I). 1/n

Create a slider a=0...1 and use the function Point(<object>,<parameter>) where the object is the polyline f and the parameter is a. You get this pink point J=Point(f,a) and you can see its trace here :
#thread 2/n

Even with a smaller increment for a, I didn't get what I wanted. So I created the Sequence :
l2=Sequence(Point(f, k), k, 0, a, 1 / 256)
shown in green which creates up to 257 points along the path when a=0...1
#thread 3/n

Then I could animate this by creating a new polyline with all these points :
g=Polyline(l2) shown in pink over l2 in green.
#thread 4/n

Better but still not as thick as I wanted. I tried several stuff to create a polygon and here's what I ended up with :
Enlarge(l2, 1.15, K) - in pink
Enlarge(l2, 0.85, K) - in yellow
creates these lists of points that I want to connect to make a polygon.
#thread 5/n

You want to start by following the pink line and then trace back following the yellow line. In order to do this I used the Reverse(<list>) function and created :
Polygon(Union(Enlarge(l2, 1.15, K), Reverse(Enlarge(l2, 0.85, K))))
Notice the function q for the opacity.
#thread 6/n

Final anim with the polyline and the opacity function for the white polygon. I wanted it to drop to 0 in the end. I started with sqrt i.e sqrt(1.5-x) that I divided by sqrt(1.5) to make it go from 1 to 0 on [0,1.5] but it decreased too fast so I changed sqrt to ^(1/4)
#thread 7/7

I realized you could do the same thing with splines instead of polylines, and it can be used to make some calligraphy.
Everything is explained in the @geogebra applet :
https://www.geogebra.org/m/zaxu6gdj 
#thread 8/7