unity clamp rotation
float rotationX = 0;
float rotationY = 0;
// you might also have some rotation speed variable
void Update() {
rotationX += Input.GetAxis("Vertical") * Time.deltaTime;
rotationX = Mathf.Clamp(rotationX, minRotationX, maxRotationX);
rotationY += Input.GetAxis("Horizontal" * Time.deltaTime;
transform.rotation = Quaternion.Euler(rotationX, rotationY, 0);
}