Well, you have to stop that bullet from acting, so like, you need to either put the return in the bullet class at a point to stop it from acting, or add code that can stop bullet from accting. you could try: public void deleteBullet(Bullet bullet) { bullet.performRemove(); } bullet's performRemove() { isRemoved = true; //declare private boolean isRemoved; in the top, } and in the bulllet's act() { if (isRemoved){ getWorld().removeObject(this); return; // this will stop bullet's execution code when it is removed. } //the rest of bullet's act method. }

Ah that error. Well, to prevent that from happening, after removing the bullet, do return; to stop execution of that bullet so that way it won't try to act when it's already out of the world.

public void checkBullet(){ if(canSee(Bulletleft.class)||canSee(Bulletright.class)) { ((Archerworld)getWorld()).deleteGuard(this); ((Archerworld)getWorld()).deleteBullet(getOneIntersectingObject(Bullet.class)); } } That will remove one bullet that is currently touching the object that calls that method.

You don't have to cast world to another one I think. getWorld().removeObjects(getWorld().getObjects(arrrow.class)); would be more correct? Just a guess. See if it compiles XD.

It starts to lag when cpu usage gets too high. Like, around when I fill the paths with little people. (How do you define lag?) Because for me, I define lag as when the framerates look like they're low (and when the movement looks choppy). Pretty good engine so far.