hugo-academic/layouts/shortcodes/spoiler.html

{{- $id := printf "spoiler-%s" (.Get "text" | lower | urlize) -}}
<div class="spoiler {{ .Get "class" }}" {{ with .Get "style" }}style="{{ . | safeCSS }}"{{ end }}>
<p>
  <a class="btn btn-primary" data-toggle="collapse" href="#{{$id}}" role="button" aria-expanded="false" aria-controls="{{$id}}">
    {{ .Get "text" }}
  </a>
</p>
<div class="collapse {{ if (eq (.Get "open") "true") }}show{{ end }}" id="{{$id}}">
  <div class="card">
    <div class="card-body">
    {{ .Inner | markdownify | emojify }}
    </div>
  </div>
</div>