How do I keep objects in fixed position when window is resized?

Question

Hello I am new to Ruby. Right now I am in the process of making a simple ping pong game using the Ruby2D to the library. My question is how do I make the two objects that are in my coat so far how do I keep them in this fixed position when I resize my window on the computer?
https://code.sololearn.com/c7QaR5c8wMJu/?ref=app