This is what I have written in the Space class. I am using the counter that was already defined I just added a CountScore function import greenfoot.*; // (World, Actor, GreenfootImage, and Greenfoot) import java.awt.Color; import java.util.List; /** * Space. Something for rockets to fly in. * * * */ public class Space extends World { private Counter scoreCounter; private int startAsteroids = 3; public Space() { super(600, 400, 1); GreenfootImage background = getBackground(); background.setColor(Color.BLACK); background.fill(); createStars(300); Rocket rocket = new Rocket(); addObject(rocket, getWidth()/2 + 100, getHeight()/2); addAsteroids(startAsteroids); scoreCounter = new Counter("Score: "); addObject(scoreCounter, 60, 380); Explosion.initializeImages(); ProtonWave.initializeImages(); } /** * Add a score to the score counter. */ public void countScore(int count) { scoreCounter.add(count); } /** * Add a given number of asteroids to our world. Asteroids are only added into * the left half of the world. */ private void addAsteroids(int count) { for (int i = 0; i < count; i++) { int x = Greenfoot.getRandomNumber(getWidth()/2); int y = Greenfoot.getRandomNumber(getHeight()/2); addObject(new Asteroid(), x, y); } } /** * Adds a specified number of stars in space. */ private void createStars(int number) { GreenfootImage background = getBackground(); for(int i = 0; i < number; i++) { int x = Greenfoot.getRandomNumber( getWidth() ); int y = Greenfoot.getRandomNumber( getHeight() ); int color = 150 - Greenfoot.getRandomNumber(100); background.setColor(new Color(color,color,color)); background.fillOval( x, y, 2, 2); } } /** * This method is called when the game is over to display the final score. */ public void gameOver() { { Greenfoot.delay(85); addObject(new ScoreBoard(scoreCounter.getValue()), getWidth()/2, getHeight()/2); } } } This is what I have written in the Asteroid class import greenfoot.*; // (World, Actor, GreenfootImage, and Greenfoot) import java.util.List; /** * A rock in space * * */ public class Asteroid extends SmoothMover { private Counter counter; /** Size of this asteroid */ private int size; /** When the stability reaches 0 the asteroid will explode */ private int stability; public Asteroid(Counter scoreCounter) { counter = scoreCounter; } public Asteroid() { this(50); } public Asteroid(int size) { super(new Vector(Greenfoot.getRandomNumber(360), 2)); setSize(size); } public Asteroid(int size, Vector speed) { super(speed); setSize(size); } public void act() { move(); } /** * Set the size of this asteroid. Note that stability is directly * related to size. Smaller asteroids are less stable. */ public void setSize(int size) { stability = size; this.size = size; GreenfootImage image = getImage(); image.scale(size, size); } /** * Return the current stability of this asteroid. (If it goes down to * zero, it breaks up.) */ public int getStability() { return stability; } /** * Hit this asteroid dealing the given amount of damage and adding the * correct amount of points. */ public void hit(int damage) { stability = stability - damage; if(stability <= 0) { breakUp (); } } /** * Break up this asteroid. If we are still big enough, this will create two * smaller asteroids and add 10 points to the score. If we are small already, * just disappear and add 25 points to the score. */ private void breakUp() { Space space = (Space) getWorld(); Greenfoot.playSound("Explosion.wav"); if(size <= 16) { getWorld().removeObject(this); space.countScore(25); // adds 25 points for removing an asteroid. } else { int r = getMovement().getDirection() + Greenfoot.getRandomNumber(45); double l = getMovement().getLength(); Vector speed1 = new Vector(r + 60, l * 1.2); Vector speed2 = new Vector(r - 60, l * 1.2); Asteroid a1 = new Asteroid(size/2, speed1); Asteroid a2 = new Asteroid(size/2, speed2); getWorld().addObject(a1, getX(), getY()); getWorld().addObject(a2, getX(), getY()); a1.move(); a2.move(); getWorld().removeObject(this); space.countScore(10); //adds 10 points for splitting an asteroid. } } }

This is a problem with that Counter class. One solution is just to stop it animating altogether, which removes the problem: use counter.setValue(counter.getValue() + amount) rather than counter.add(amount). Or you can get the scoreboard to make sure the counter shows the final result: the slightly odd code counter.setValue(counter.getValue()) will actually do this.

Don't use Greenfoot.delay(...) as, like you noticed, it delays everything. You need to introduce a counter/timer which you decrement (or increment) every act, until it times out, and then you put the scoreboard in the world.