private void LateUpdate () {
    Vector3 cameraPosition = this.transform.position;
    Vector3 targetPosition = target.transform.position;

    Vector3 idealTargetPosition = this.mainCamera.ViewportToWorldPoint (target.ViewportPosition);
    Vector3 offset = cameraPosition - idealTargetPosition;
        
    cameraPosition.x = targetPosition.x + offset.x;
    this.transform.position = cameraPosition;
}