问从可折叠Bootstrap卡中删除边框

EN

.card {
    border: 0;
}

<div class="card border-0">...</div>

.card.card-body{ border:none; }

 .btn-primary.focus, .btn-primary:focus { box-shadow:unset !important;}
 
 .btn.focus, .btn:focus{ box-shadow:unset !important;}

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">

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    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
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<div id="skills" class="showcase-buttons">
      <button type="button" class="btn btn-primary btn-block" 
        data-toggle="collapse" href="#skills-showcase" aria-expanded="false"
        aria-controls="skills-showcase">
        Skills
      </button>

      <!-- collapsible content (skills) -->
      <div id="skills-showcase" class="collapse showcase-content justified-text">
        <div class="row justify-content-around">
          <div class="col-md-4">
            <div id="computer-skills">
              <div class="card card-body">
                <h3>Computer</h3>
                <p>
                  We'll put some happy little leaves here and there. If we're going to
                  have animals around we all have to be concerned about them and take
                  care of them. As trees get older they lose their chlorophyll. This
                  present moment is perfect simply due to the fact you're experiencing
                  it. Let's make some happy little clouds in our world.
                </p>
              </div>
            </div>
          </div>
          <div class="col-md-4">
            <div id="design-skills">
              <div class="card card-body">
                <h3>Design</h3>
                <p>
                  Put it in, leave it alone. Just let go - and fall like a little
                  waterfall. The more we do this - the more it will do good things to
                  our heart. Nature is so fantastic, enjoy it. Let it make you happy.
                  Trees grow in all kinds of ways. They're not all perfectly straight.
                  Not every limb is perfect. There are no limits in this world.
                </p>
              </div>
            </div>
          </div>
          <div class="col-md-4">
            <div id="problem-solving-skills">
              <div class="card card-body">
                <h3>Problem Solving</h3>
                <p>
                  If these lines aren't straight, your water's going to run right out of
                  your painting and get your floor wet. And I will hypnotize that just a
                  little bit. You need the dark in order to show the light. We don't
                  really know where this goes - and I'm not sure we really care. I get
                  carried away with this brush cleaning.
                </p>
              </div>
            </div>
          </div>
        </div>
      </div>
    </div>