.enter_btn {
  display: inline-block;
  width: 250px;
  text-align: center;
  text-decoration: none;
  line-height: 60px;
  outline: none;
  color: #6894FF;
  background-color: #f5f5f5;
  position: relative;
  border: 1px solid #6894FF;
  transition: color 0.5s ease;
}
.enter_btn:hover {
  color: #f5f5f5;
}
.enter_btn:hover::before {
  transform: scaleY(1);
}
.enter_btn:before {
  position: absolute;
  top: 0;
  left: 0;
  content: "";
  display: block;
  width: 100%;
  height: 100%;
  background: #6894FF;
  transform: scaleY(0);
  transition: all 0.5s ease;
  transition-property: transform;
}