Why are screenX and screenY relevant here as far as their code goes?
Where they using those values in their code?
Very interesting article but I'm missing the step where it would impact their code ...
 replies(1): 
  (() => {
    const logEvent = event => console.log({
      coords: [event.screenX, event.screenY],
      type: event.type
    });
    const input = document.querySelector("textarea");
    // use "keydown" instead of "keypress" to detect all keyboard input instead of just character producing input 
    input.addEventListener("keydown", logEvent);
    input.addEventListener("click", logEvent);
  })();