<section>
  <div class="btn btn__07">
    <a href="#">1-7.下から幕が上がる</a>
  </div>
</section>
section{
  display: flex;
  margin:2rem;
  justify-content: center;
  align-items: center;
}
.btn a {
  display: inline-block;
  text-decoration: none;
  border: 2px solid #333;
  color: #333;
  padding: .7rem 1.5rem;
  transition: .2s;
}

.btn.btn__07 a {
  overflow: hidden;
  position: relative;
  transition: .3s;
}

.btn.btn__07 a:before {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  margin: auto;
  width: 100%;
  height: 0;
  background-color: #2382e5;
  z-index: -1;
  transition: .3s;
}

.btn.btn__07 a:hover {
  transition: .3s;
  color: white;
}

.btn.btn__07 a:hover:before {
  height: 100%;
}

External CSS

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External JavaScript

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