Hey,
after looking at the script for a while and wondering why you subtract and add startPos in the first place, I realized that we actually just want to multiply the camera position with the parallaxOffset to get our Parallax effect.
So I simplified the script a little bit and removed the startPos and travel variable/property:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class Parallax : MonoBehaviour
{
[SerializeField] private float parallaxOffset = -0.15f;
private Camera cam;
private void Awake() {
cam = Camera.main;
}
private void FixedUpdate() {
transform.position = cam.transform.position * parallaxOffset;
}
}