Curtain Down

.btn-curtain-down {
  position: relative;
  z-index: 0;
  overflow: hidden;
  display: inline-block;
  padding: 12px 26px;
  border: 2px solid #8b5cf6;
  border-radius: 10px;
  background: transparent;
  color: #8b5cf6;
  font-family: inherit;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: color 0.3s ease;
}
.btn-curtain-down::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  border-radius: 8px;
  background: #8b5cf6;
  transform: scaleY(0);
  transform-origin: top;
  transition: transform 0.3s ease;
}
.btn-curtain-down:hover {
  color: #ffffff;
}
.btn-curtain-down:hover::before {
  transform: scaleY(1);
}