Hydro/packages/ui-default/templates/partials/problem_lucky.html

<div data-fragment-id="problem_lucky">
  <p>
    <a href="{{ url('problem_random', query={category:category}) if category else url('problem_random') }}" class="expanded button" target="_blank">
      <span class="icon icon-feeling-lucky"></span> {{ _('Lucky') }}
    </a>
  </p>
  <div class="typo supplementary">
    <p>{{ _('Pick a problem randomly based on current filter') }}</p>
  </div>
</div>