public class BarrelMovement : MonoBehaviour
{
    // Update is called once per frame
    void Update()
    {
        Vector3 mousePosition = Camera.main.ScreenToWorldPoint(Input.mousePosition);
        mousePosition = new Vector3(mousePosition.x, mousePosition.y, 0);

        Vector3 barrelPosition = transform.position;

        transform.up = mousePosition - barrelPosition;
    }
}