.btn-top-left {
  position: fixed;
  top: 16px;
  left: 16px;
  background: transparent;
  color: white;
  font: 600 20px/1 monospace;
  border: none;
  padding: 4px 8px;
  cursor: pointer;
  text-decoration: none;
  opacity: 0.8;
  transition: opacity 0.2s ease;
}
.btn-top-left:hover {
  opacity: 1;
}