public static boolean is_valid (Circle c1){
		boolean valid = true;
		for (Circle c2 : circles){
			if (intersect(c1, c2)){
				valid = false;
				break;
			}
		}
		
		if (c1.center_x >  c1.radius && c1.center_x < (PANEL_WIDTH - c1.radius));
		else
			valid = false;
		if (c1.center_y >  c1.radius && c1.center_y < (PANEL_HEIGHT - c1.radius));
		else
			valid = false;
		return valid;
	}