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

Maybe try with this

rigidbody.AddForce(new Vector3(Input.GetAxis("Vertical") * XSpeed,  0.0f, Input.GetAxis ("Horizontal") * ZSpeed), ForceMode.Impulse);

If you look on the Input Manager, Vertical is use to get W and S key, Horizontal is A and D
API reference: Input Manager