Unity implements desktop bounce sample code

using UnityEngine;
 
public class Ball : MonoBehaviour
{
    private Rigidbody rigid;
 
    private Vector3 lastDir;
 
    public float speed = 30;
 
    private void Awake()
    {
        rigid = GetComponent<Rigidbody>();
 
        rigid.velocity = new Vector3(1, 0, 1) * speed;
    }
 
    private void LateUpdate()
    {
        lastDir = rigid.velocity;
    }
 
    private void OnCollisionEnter(Collision other)
    {
        if (other.gameObject.tag == "Wall")
        {
            Vector3 reflexAngle = Vector3.Reflect(lastDir, other.contacts[0].normal);
            rigid.velocity = reflexAngle.normalized * lastDir.magnitude;
        }
    }
}