OK, your x and y are where in the world background you want your star; good so far. Your GreenfootImage image will be a star; ok here. Setting the draw color for the star to white; still good. Using fillOval on the image with oval width 2 and height 2 to be drawn at x and y; now we got problems. First off, x and y are the coordinates in the background image where you want the star, not coordinates of the image, like this method needs. Instead of using 'fillOval', just use 'fill, as the image is only 2 x 2 to begin with. Next, what you need is to use the 'drawImage' method to actually put the star on the background image (we will get to that in a minute). The last statement 'setBackground(image);' is not what you want either; as that will make your star the backgound image. You want your background image with stars. The last thing is this: all of your stars are the same size and use the same basic image; let us simplify the code by moving that outside the 'for' loop. As such:

Of course, this works too:

Hi Danpost I have a question. have can u make so the stars to move to the right and when it hits the edge it dissapears and a new star will pop in the same place but in the left side?

You will need two instance world fields, besides the one that holds the number of stars to place in the world; one to hold the background image and another to track the offset of the image in the background. Let your world constructor create the initial image and save it in the GreenfootImage field or call a method to do so. The act() method in your world should call a method to deal with the scrolling of the background. That method should increment the offset and create and set the new image for the background. The stars will then re-appear on the left when they disappear on the right.

Yeah, I found three things wrong with it (1) Line 21: change 'bgImg.fillOval(2, 2, x, y);' to 'bgImg.fillOval(x, y, 2, 2);' (2) Line 33: change the period '.' to a comma ',' (3) Line 34: change 'setImage' to 'setBackground'

If your started the scenario and they do not move, then it must be something else in your code. I created a new scenario with only the code above (with the three fixes) and when I ran it, it worked properly. The stars move from left to right and re-appear at the left.

Here is my code import greenfoot.*; // (World, Actor, GreenfootImage, Greenfoot and MouseInfo) import java.awt.Color; /** * Write a description of class SpaceWorld here. * * @author (your name) * @version (a version number or a date) */ public class SpaceWorld extends World { int color; GreenfootImage bgImg = null;// holds main image int bgX;//tracks offset of image in background final int starCount = 100;// change as desired /** * Constructor for objects of class SpaceWorld. * */ public SpaceWorld() { // Create a new world with 600x400 cells with a cell size of 1x1 pixels. super(600, 400, 1); createBackgroundImage(); } public void act() { scrollBackground(); } public void createBackgroundImage() { bgImg = new GreenfootImage(getWidth(), getHeight()); bgImg.setColor(Color.black); bgImg.fill(); bgImg.setColor(Color.WHITE); for( int i = 0; i< starCount; i++) { int x = Greenfoot.getRandomNumber(getWidth()); int y = Greenfoot.getRandomNumber(getHeight()); bgImg.fillOval(x,y,2,2); } setBackground(bgImg); } public void scrollBackground() { bgX = (bgX + 1) % getWidth(); GreenfootImage img = new GreenfootImage(getWidth(), getHeight()); img.drawImage(bgImg, bgX,0); img.drawImage(bgImg, bgX - getWidth(),0); } }

You are missing the last statement in the scrollBackground() method You have declared and 'int color' variable in the world class, yet you are not using it (just to let you know)