Gravity

import greenfoot.*;

/**
 * Write a description of class robot here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class robot extends Actor
{
    private int balloonEaten = 0;
    private Counter counter;
    private skull skull;
    private int vSpeed = 0;
    private int acceleration =2;
    private int setLocation;
    
    public robot(Counter pointCounter)
    {
        counter = pointCounter;
    }
    
    public void act() 
    {   
        checkFall();
        if (Greenfoot.isKeyDown("shift"))
        Greenfoot.start();
        if (Greenfoot.isKeyDown("enter"))
        Greenfoot.stop();
        if (Greenfoot.isKeyDown("right"))
        move(5);
        if (Greenfoot.isKeyDown("left"))
        move(-5);
        if (Greenfoot.isKeyDown("space"))
        turn(17);
        setRotation(90);
        if (Greenfoot.isKeyDown("up"))
          { move(-5); }
        if (Greenfoot.isKeyDown("down"))
          { move(5); }
        setRotation(0);
        if (isAtEdge() )
        {
            turn(90);
         }
         Actor balloon = getOneIntersectingObject(balloon.class);
        if(balloon != null)
        {
            World myWorld = getWorld();
            balloonEaten++;
            counter.add(1);
            Greenfoot.playSound("balloon pop.mp3");
            myWorld.removeObject(balloon);
            myWorld.addObject(new Explosions(),getX(),getY());
            if (counter.getValue() >= 9) {
                gameOver();
            }
            if (balloonEaten >= 10) {
                YouWin youwin = new YouWin();
                myWorld.addObject(youwin, myWorld.getWidth()/2, myWorld.getHeight()/2);
            }
            if (balloonEaten >= 1) {
                skull skull = new skull(counter);
                myWorld.addObject(skull, Greenfoot.getRandomNumber(myWorld.getWidth()), Greenfoot.getRandomNumber(myWorld.getHeight()));
            }
        }
    }
    
    private void fall()
    {
      setLocation(getX(), getY(), +vSpeed);
      vSpeed = vSpeed + acceleration;
    }
    
    public boolean onGround()
    
    {
        int spriteHeight = getImage().getHeight();
        int lookForGround = (int)(spriteHeight/2) + 5;
        
        Actor ground = getOneObjectAtOffset(0, lookForGround, road.class);
        
        if(ground == null)
        {
            return false;
        }
        else
        {
            return true;
        }
    }
    
    public void checkFall()
    {
        if(onGround())
        {
            vSpeed =0;
        }
        else
        {
            fall();
        }
    }
    
    /**
     * We have won the game.
     */
    public void gameOver()
    {
        Greenfoot.playSound("superstition.wav");
        Greenfoot.stop();
    }
}

      setLocation(getX(), getY(), +vSpeed);