Spaceship movement script?

I was practicing my java with a ship script, feel free to use it. I am more familiar with C# so I wasn't sure about how to use the Input.mousePosition in javascript, so you'll get an error saying:

 INTERNAL_get_mousePosition is not allowed to be called from a MonoBehaviour constructor (or instance field initializer), call it in Awake or Start instead. Called from MonoBehaviour 'ship_control' on game object 'Player'.
 See "Script Serialization" page in the Unity Manual for further details.
 

But anyways, a basic, uncluttered system, and it works, I made one for C# but can't find it. Here's the javascript (ship_control.js), just add it to your 'Player' object and then attach the camera as a child of the 'Player'. You can also add a 3D model of a spaceship as a child of the 'Player' object too.

 public var MousePosition = Input.mousePosition;
 public var position;
 public var curShipSpeed : float = 0.0;
 public var step = 2;
 public var current_speed = 0;
 public var maxSpeed : int = 100;
 public var mouse_rotate = 0.5;
 public var agility = 30;
 public var dist_fr_ship = 2.85;
 public var rotate_speed = 2.0;
 
 function Update () {
 
         if (Input.GetKey ("d")) 
         {
             transform.Rotate(0,0,-rotate_speed);
         }
 
         if (Input.GetKey ("a")) 
         {
             transform.Rotate(0,0,rotate_speed);
         }
         if ((Input.GetKey("up") || Input.GetKey("w")) && (current_speed < maxSpeed)) {
         current_speed += step;
     } else if ((Input.GetKey("down") || Input.GetKey("s"))  && (current_speed > 0)) {
         current_speed -= step;
     }
 
         MousePosition = Input.mousePosition;
         MousePosition.x = (Screen.height/2) - Input.mousePosition.y;
         MousePosition.y = -(Screen.width/2) + Input.mousePosition.x;
         transform.Rotate(MousePosition * Time.deltaTime * mouse_rotate, Space.Self);
 
     curShipSpeed = Mathf.Lerp(curShipSpeed, current_speed, Time.deltaTime * step);
     transform.position += transform.TransformDirection(Vector3.forward) * curShipSpeed * Time.deltaTime;
     
 }