Using WASD keys instead of mouse to roll ball?

Hey,

I am trying to use the W and S key in order to control a cube which I am just using for a demo... Below is the code I have found which allows me to use the mouse to move the cube and hit the Sphere... How can I make it so the cube is moved with WASD?

using UnityEngine; using System.Collections;

[RequireComponent(typeof(Rigidbody))]

public class SphereMovement : MonoBehaviour { float ZSpeed = 1.0f; float XSpeed = 1.0f;

 void Start()
 {
     rigidbody.freezeRotation = true;
     rigidbody.drag = 5.0f;
     Physics.maxAngularVelocity = 100.0f;
 }
 
 void Update()
 {
     rigidbody.AddForce(new Vector3(Input.GetAxis("Mouse X") * XSpeed
                                    0, Input.GetAxis ("Mouse Y") * ZSpeed), ForceMode.Impulse);
 }
 
 void OnCollisionEnter(Collision other)
 {
     if(other.rigidbody)
     {
         if(!other.gameObject.GetComponent<ConstantForce>())
             other.gameObject.AddComponent<ConstantForce>();
         else
             other.rigidbody.constantForce.force = rigidbody.velocity;
     }
 }
 

}

Thanks, John