public function isOutdated()
    {
        $this->boot();

        $compiled_tracked_files = new TrackedFiles([$this->output_dir]);
        $current_tracked_files  = new TrackedFiles($this->paths);

        if ($current_tracked_files->modifiedAfter($compiled_tracked_files)) {
            $this->profiler->set('tracker.reason', 'One of the tracked files has been modified.');
            return true;
        }

        $this->profiler->set('tracker.reason', false);
        return false;
    }