Rendering error in this graph

[MarksonChen]

There's a weird glitch when trying the drag the graph in this link: https://www.math3d.org/vFJBApnJ Also, x and y are both defined to be <π and >-π, but it seems that the calculator rendered parts that are outside of the defined region:

[Zaq-Xander]

Hey, I've taken a look and compiled some thoughts into this document: https://www.math3d.org/9frRYIAjr. Everything that I have to say is said inside the document; take a look around :)