public Vector limitPosition(Vector position, World world) {
int halfScreenWidth = Engine.getInstance().getWidth() / 2, halfScreenHeight = Engine
.getInstance().getHeight() / 2;
Vector re = position;
if (position.x < halfScreenWidth) {
re = re.modifyX(halfScreenWidth);
}
if (position.y < halfScreenHeight) {
re = re.modifyY(halfScreenHeight);
}
if (position.x > world.width - halfScreenWidth) {