Define you variables, summarize the steps needed and formulate the specific conditions that would be required to do the individual steps involved. Work on one step at a time. If and when you run into difficulties in coding it, post what you tried and ask for help on the specific step at hand.

Sorry but I figured it out. This is my code for it. import green foot. Thx for replying. *; /** * Write a description of class ball here. * * @author (your name) * @version (a version number or a date) */ public class ball extends Actor { /** * Act - do whatever the Skelaton wants to do. This method is called whenever * the 'Act' or 'Run' button gets pressed in the environment. */ /** * An example of a method - replace this comment with your own * * @param y a sample parameter for a method * @return the sum of x and y */ private int gravity = 0; public void act() { if (onGround() && Greenfoot.isKeyDown("up")) { System.out.println("Actor should jump"); System.out.println("Actor at: (" + getX() + ", " + getY() + ")"); jump(); // Add your action code here. } if (Greenfoot.isKeyDown("right")) { move (3); } if (Greenfoot.isKeyDown("left")) { move (-3); } checkFall();//fill this in with what you want, //but add this here: if (onGround() && Greenfoot.isKeyDown("up")) { jump(); checkFall(); } } private void checkFall() { if(!onGround() || gravity < 0) fall(); } private boolean onGround() { int myHeight = getImage().getHeight(); Actor ground = getOneObjectAtOffset(0, myHeight/2, Ground.class); if(ground != null)//if the ground is really there... return true; //(if not, return false) return false; } //this is quite like SPower's method private void fall() { setLocation(getX(), getY() + gravity); gravity++;//the player will accelerate as he falls } private void jump() { gravity -= 20;//or choose 10 or 15 or whatever works } }