Why my code doesnt work?

Question

Why does it not work? It should create element right on element "arrow" but it says error...

https://code.sololearn.com/WSiFB6TheVJp/?ref=app

Answer 1

from what i've seen the start button is changing the speed of the line. if i press it several times it accelerates a few times, then it deccelerates and so on.
it seems that the variable speed is not doing much.

Answer 2

Yep ik about start button issue. It just calls the function more times. And when u call it while the opposite function is running it decreases speed.

I need to know why doesnt speed var do anything...