private boolean isInsideWorld() {
		// Check it is inside the world
		if (x<0 || y<0 || x+width>=_world.getWidth() || y+height>=_world.getHeight()) {
			// Adjust direction
			if (x < 0 || x + width >= _world.getWidth())
				dx = -dx;
			if (y < 0 || y + height >= _world.getHeight())
				dy = -dy;
			dtheta = 0;
			return false;
		}
		return true;
	}