.container {
  font-family: "Yu Gothic", YuGothic, Verdana, 'Hiragino Kaku Gothic ProN','Hiragino Kaku Gothic Pro', 'ヒラギノ角ゴ Pro W3', 'メイリオ', Meiryo, sans-serif;
  text-align: center;
  padding-top: 40px;
  padding-bottom: 40px;
  background: #000;
}

.btn-box {
  display: inline-block;
  width: 200px;
  text-align: center
  font-size: 16px;
  color: #9ec34b;
  text-decoration: none;
  font-weight: bold;
  padding: 12px 24px;
  position: relative;
  border: 2px solid #9ec34b;
  transition: .4s;
}

.btn-box:hover {
  border: 2px solid transparent;
  color: #FFF;
}

.btn-box:before, .btn-box:after {
  width: 100%;
  height: 100%;
  z-index: 3;
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  box-sizing: border-box;
  transform: scale(0);
  transition: .2s;
}

.btn-box:before {
  border-bottom: 2px solid #FFF;
  border-left: 2px solid #FFF;
  transform-origin: 100% 0%;
}

.btn-box:after {
  border-top: 2px solid #FFF;
  border-right: 2px solid #FFF;
  transform-origin: 0% 100%;
}

.btn-box:hover:after,
.btn-box:hover:before {
  transform: scale(1);
}