CODE EXAMPLE FOR CSHARP

Unity Make a 2D object look at the mouse position

public class LookAtMouse : MonoBehaviour
{
    void Update()
    {
        Vector3 mousePosition = Camera.main.ScreenToWorldPoint(Input.mousePosition);
        
        Vector2 direction = mousePosition - transform.position;
        float angle = Vector2.SignedAngle(Vector2.right, direction);
        transform.eulerAngles = new Vector3 (0, 0, angle);
    }
}