stops game

import greenfoot.*; // (World, Actor, GreenfootImage, Greenfoot and MouseInfo) public class M extends Animal { public void act() { removeM(); turnatEdge(); move(); } public void removeM() { if(Greenfoot.mouseClicked(this)) { getWorld().removeObject(this); } } public void turnatEdge() { if ( atWorldEdge() ) { turn(17); } } }

In your 'act' method, you are calling 'removeM' first; then calling 'turnatEdge' and 'move', both of which require that the object be in the world. If 'removeM' removes the object from the world, 'turnatEdge' will error. An easy fix would be to rearrange the method calls in your act method.

Also, can you help me with this as well? I'm trying to get my object to move left, if it hits the right edge of the world, move right, if it hits the left edge of the world, move down if it hits the top edge, and move up if it hits the right edge. This is the method:....but when it hits the right edge, for example, it moves left but then right again...because I have move(); in the act method. public void turnatEdge() { if ( atLeftEdge() ) { setLocation(getX()+2, getY()); } if (atRightEdge()) { setLocation(getX()-2, getY()); } if (atBottomEdge()) { setLocation(getX(), getY()-2); } if (atTopEdge()) { setLocation(getX(), getY()+2); } } Thanks, I really appreciate your help.

What you need to do is either control the rotation of the object so that the call to the 'move' method will move the object in the proper direction or keep track of the speed of the object in both the x and y directions. With either method, the proper adjustments to the rotation or value of the variables are needed when the object hits the walls.