Move your mouse. Adjust both sliders to change the length of both individual segments on the arm Try it here: phosphorus.github.io/#65363358 If the arm lengths are not the same then your mouse can get too close to the center and the tip of the arm won't reach.
Second Test for a project I am working on. Based on https://scratch.mit.edu/projects/65356436 To understand how it works, look at my project linked above. (this is very similar, but NOT the same) Feel free to use with credit! :)