Try changing line 15 of the act method in the PumpkinPieShip class to:

/** * */ public class PumpkinPieShip extends SpaceActors { private int horizontalSpeed = 0; private int verticalSpeed = 0; World myWorld = getWorld(); public void act() { bounceAtEdge(); turnOnCommand(); accelOnCommand(); move(horizontalSpeed,verticalSpeed); } public void turnOnCommand() { if(Greenfoot.isKeyDown("down")) { setRotation(90); } if(Greenfoot.isKeyDown("up")) { setRotation(270); } if(Greenfoot.isKeyDown("right")) { setRotation(360); } if(Greenfoot.isKeyDown("left")) { setRotation(180); } if(Greenfoot.isKeyDown("down")) { move(5); } if(Greenfoot.isKeyDown("up")) { move(5); } if(Greenfoot.isKeyDown("left")) { move(5); } if(Greenfoot.isKeyDown("right")) { move(5); } } public void accelOnCommand() { if (Greenfoot.isKeyDown("space")) { int rot=getRotation(); if(rot == 0) { horizontalSpeed = horizontalSpeed +1; } else if(rot == 180) { horizontalSpeed = horizontalSpeed -1; } else if(rot == 270) { verticalSpeed = verticalSpeed -1; } else if(rot == 90) { verticalSpeed = verticalSpeed +1; } } } public void move(int changeX, int changeY) { int x = getX(); int y = getY(); int newX = x + changeX; int newY = y + changeY; setLocation(newX,newY); } public String hitTheEdge() { int x = getX(); int y = getY(); int bottomSide = myWorld.getWidth() - 1; int rightSide = myWorld.getHeight() -1; if(y == 0) { return "top"; } else if (x == 0) { return "left"; } else if(x == rightSide) { return "right"; } else if(y == bottomSide) { return "bottom"; } else { return null; } } public void bounceAtEdge() { String edge = hitTheEdge(); if(edge == "top" || edge == "bottom") { verticalSpeed = verticalSpeed * -1; } else if (edge == "left" || edge == "right") { horizontalSpeed = horizontalSpeed * -1; } } }

'myWorld' will always be null because 'getWorld()' is executed before the object is added to a world. You can either remove the line and change every 'myWorld' instance to 'getWorld()', or you can add this method:

Or move the line: to be the first line in the hitTheEdge method.