Move the mouse pointer and the snakey thing will follow.
Simple animation experiment with stamping. It also uses List variables to keep track of the prior X/Y positions of the circle so they can follow along like a snake. The loop that draws the stamps uses a custom block with the "Draw without Refresh" option. With that option turned off, the loop in the custom block runs so slowly that the animation doesn't appear smooth at all. (Scratch by default builds a delay into each repetition of a loop.)
