the speed is a negative number because it moves backwards on the x-axis the speed is a positive number if it moves forwards on the x-axis (to the right)

use setLocation and give the editor your coordinates, here is the code of the asteroids: import greenfoot.*; // (World, Actor, GreenfootImage, Greenfoot and MouseInfo) import java.util.Random; /** * Write a description of class meteoriet here. * * @author (your name) * @version (a version number or a date) */ public class meteoriet extends Actor { Random r = new Random(); private int speed = -2; /** * Act - do whatever the meteoriet wants to do. This method is called whenever * the 'Act' or 'Run' button gets pressed in the environment. */ public void act() { move(speed); if (this.isAtEdge()) { this.setLocation(550, r.nextInt(50)+100); speed = speed-1; } Actor raket = this.getOneIntersectingObject(raket.class); if (raket != null) { //(this.getWorldOfType(MyWorld.class)).getHealthbar().loseHealth(); Healthbar Hb = (this.getWorldOfType(MyWorld.class)).getHealthbar(); Hb.loseHealth(); this.setLocation(550, r.nextInt(50)+100); if (Hb.Health==0) { (this.getWorldOfType(MyWorld.class)).einde_spel(); this.getWorld().removeObject(raket); World myWorld = getWorld(); Game_over gameover = new Game_over(); myWorld.addObject(gameover, myWorld.getWidth()/2,200);} }// Add your action code here. Actor a = this.getOneIntersectingObject(Laser.class); if (a != null) { // this.getWorld().removeObject(this); this.setLocation(550, r.nextInt(300)+50); } } }