@php
  $output_category_id = get_queried_object_id();
@endphp

@if (have_posts())
  <div class="posts">
    @while (have_posts()) @php the_post() @endphp
      @php
        $category_id = get_the_category()[0]->term_id;
      @endphp
      @if ( $output_category_id == $category_id )
        <article class="panel">
          <div class="panel-heading">
            <h2 class="panel-title"><a href="@php the_permalink() @endphp">@php the_title() @endphp</a></h2>
          </div>
          <div class="panel-body clearfix">
            @php
              the_post_thumbnail( 'thumbnail' , ['class' => 'alignright'] );
              the_excerpt();
            @endphp
            <a href="@php the_permalink() @endphp" class="button button-green">Read Full Article</a>
          </div>
        </article>
      @endif
    @endwhile
  </div>
@endif