public static function wait(int $seconds, bool $countdown = false)
	{
		if ($countdown === true)
		{
			$time = $seconds;

			while ($time > 0)
			{
				fwrite(STDOUT, $time . '... ');
				sleep(1);
				$time --;
			}
			static::write();
		}
		else
		{
			if ($seconds > 0)
			{
				sleep($seconds);
			}
			else
			{
				// this chunk cannot be tested because of keyboard input
				// @codeCoverageIgnoreStart
				static::write(static::$wait_msg);
				static::input();
				// @codeCoverageIgnoreEnd
			}
		}
	}