Sidescroller, rotating via mouse control

Okay, lets cut to the chase. I am making a sidescroller game where my character is controlled left and right by A and D. The player can press W to jump and has the ability to press space to slow down time. I want to add a new aspect though, where the player can shoot and aim with the mouse (just like in this video):

• http://www.youtube.com/watch?v=f_bV_n4dOhA&feature=BFa&list=HL1337156253

Here is the script for character movement and jumping so far:

 var speed = 6.0;
 
 var jumpSpeed = 8.0;
 
 var gravity = 20.0;
 
  
 
 private var moveDirection = Vector3.zero;
 
 private var grounded : boolean = false;
 
 private var lastYSpeed : float = 0;
 
  
 
 function FixedUpdate() {
 
    if (grounded)
 
    {
 
       // We are grounded, so recalculate movedirection directly from axes
 
       moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));
 
       moveDirection = transform.TransformDirection(moveDirection);
 
       moveDirection *= speed;
 
       
 
       if (Input.GetButton ("Jump")) {
 
          moveDirection.y = jumpSpeed;
 
       }
 
       
 
       // On the ground
 
       lastYSpeed = 0;
 
    }
 
    else
 
    {
 
       // We are in the air, maintain lastYSpeed
 
       moveDirection = new Vector3(Input.GetAxis("Horizontal"), lastYSpeed, Input.GetAxis("Vertical"));
 
       moveDirection = transform.TransformDirection(moveDirection);
 
       
 
       // Remove speed factor from influencing Y value
 
       moveDirection.x *= speed;
 
       moveDirection.z *= speed;
 
    }
 
  
 
    // Apply gravity
 
    moveDirection.y -= gravity * Time.deltaTime;
 
    lastYSpeed = moveDirection.y;
 
    
 
    // Move the controller
 
    var controller : CharacterController = GetComponent(CharacterController);
 
    var flags = controller.Move(moveDirection * Time.deltaTime);
 
    grounded = (flags & CollisionFlags.CollidedBelow) != 0;
 
 }
 
  
 
 @script RequireComponent(CharacterController)

Thank you SO MUCH in advance, really apreciate it :)