<div class="container">
  <a class="btn-sizechange" href="#">
    <span>PUSH ME</span>
  </a>
</div>
/* ここはコピーしなくてOK */
.container {
  @import url('https://fonts.googleapis.com/css2?family=Noto+Sans+JP:wght@700&display=swap');
  font-family: 'Noto Sans JP', sans-serif;
  text-align: center;
  padding-top: 40px;
}

/* ここから下がボタンのCSS */
.btn-sizechange {
  display: inline-block;
  text-decoration: none;
  font-weight: 700;
  color: #65A04D;
  text-align: center;
  width: inherit;
  min-width: 188px;
  border: 2px solid #65A04D;
  padding: 12px 16px;
  position: relative;
  opacity: 1 !important;
  transition: all 0.3s;
}
.btn-sizechange:after {
  content: "";
  display: block;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 0;
  height: 0;
  opacity: 0;
  background-color: #65A04D;
  transition: all 0.3s;
  pointer-events: none;
}
.btn-sizechange span {
  position: relative;
  z-index: 99;
}
.btn-sizechange:hover {
  color: #FFF;
  transform: scale(0.9);
}
.btn-sizechange:hover:after {
  width: 100%;
  height: 100%;
  opacity: 1;
}

External CSS

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External JavaScript

This Pen doesn't use any external JavaScript resources.