merge css and scss in laravel mix

This is my code:

mix.js('resources/assets/js/app.js', 'public/js')
   .sass('resources/assets/sass/app.scss', 'resources/assets/css')
   .styles([
     'resources/assets/css/animate.min.css'
   ],'resources/assets/css/style.css')
   .combine(['resources/assets/css/style.css','resources/assets/css/app.css'], 'public/css/app.css');

and results:

\js\app.js   928 kB

\resources\assets\css\app.css   185 kB

\resources\assets\css\style.css  52.8 kB

\css\all.css  52.8 kB

 You can see,It can merge app.css with style.css. output is only style.css as all.css

what is wrong?

via Chebli Mohamed