My Unity 2D platoformer shooter question.

I want to make platofmer shooter game to develop myself.My control script here,

 var speed = 25.0f;
 var health = 5;
 var dmg = 1;
 var X : float;
 
 var firePrefab : Transform;
 var barrelEnd : Transform;
 
 function Start(){
     X = transform.localScale.x;
 }
 function Update () {
     if(Input.GetKey(KeyCode.D)){
         transform.position.x += speed * Time.deltaTime;
         transform.localScale.x = X;
         
     }
     
     if(Input.GetKey(KeyCode.A)){
         transform.position.x -= speed * Time.deltaTime;
         transform.localScale.x = -X;
         
     }
     
     if(Input.GetKey(KeyCode.W)){
         transform.position.y += speed * Time.deltaTime;
     }
     
     
     if(health == 0){
         Application.LoadLevel(0);
     }
     
     if(Input.GetKey(KeyCode.Space)){
         Instantiate(firePrefab, barrelEnd.position, barrelEnd.rotation);
         ;
     }
     
     
     
 }
 
 function OnCollisionEnter(col : Collision){
     
     if(col.gameObject.name == "EnemyRight"){        
         health -= dmg;
         Debug.Log("Your health:" + health);
     }
     
     if(col.gameObject.name == "EnemyLeft"){        
         health -= dmg;
         Debug.Log("Your health: " + health);
     }
     
 }

I want to make gun system but I stay plugged here :( I make gun movement ex:

transform.position.x += speed * Time.deltaTime;

but it always move right but i want when i flip my player I want it move left :/ I hope you understand what I tell.

Thanks. :)