public class Alien extends Actor
{
 
    protected int delayCounter;   //Counts cycles.
    protected int counter;             //Another counter variable.
    public int modulus;                // make aliens move.
    public boolean first;              //first move cycle then true.
    public boolean Left;               // Alien movement to the left = true. 
    
    /**
     * Allows the Alien to be destroyed by shooter bullet.
     */
    public void act() 
    {
        Actor bullet = getOneIntersectingObject(Bullet.class);
        if(bullet != null)
        {
            getWorld().removeObject(this);
        }
        delayCounter++;
        
    }    
    
    /**
     * Allows the Alien to shoot
     */
    public void shoot ()
    {
        getWorld().addObject (new AlienBullet(), getX(), getY());
    }
       
                
    /**
     * Where each veriable is set.
     */
    public Alien()
    {
        delayCounter = 0; 
        Left = true;
        modulus = 20;
        counter = 0;
        first = true;
     
    }
    
    
    
    
    /**
    * This method tells the Alien how to move
    */
    public void move()
    {
       counter++;   
       if (counter < (20 * modulus) && first) //Go left if counter is less than 400
                                       
       {
           moveLeft();
       }
       else if (counter < (35 * modulus) && !Left && !first ) //Go right if counter
                                                                //is less than 750 and
                                                              
                                                             
       {
            moveRight();
       }
       else if (counter < (35 * modulus) && Left && !first ) //Go left if counter is
                                                               //less than 700
                                                             
                                                             
                                                               
       {
            moveLeft();
       }
        
       if ( counter == (35 * modulus) ) //Tells the aliens to move down
                                        
       {
            moveDown();
            counter = 0;
            Left = !Left;
       }
       else if (counter == (20 * modulus) && first) //Tells the aliens to move down 
                                                    //once it hits the left edge of te world
                                                 
       {
           moveDown();
           first = false;
           counter = 0;
           Left = !Left;
       }
    }
    
    /**
     * This Tells the Aliens to move left
     */
    public void moveLeft()
    {
        if ( (delayCounter % modulus) == 0)
        {
            setLocation(getX()-10, getY());
        }
    }
    
    /**
     * this tells the aliens how to go right
     */
    public void moveRight()
    {
       if ( (delayCounter % modulus) == 0)
        {
            setLocation(getX()+10, getY());
        }
    }
    
    /**
     * This shows the aliens how to go down
     */
   public void moveDown()
   {
         setLocation(getX(), getY() + 10);
   }
    
  
}