.btn {
  display:inline-block; padding:.6rem 1rem; border-radius:.5rem;
  text-decoration:none; font-weight:600; border:1px solid #444;
}
.btn--primary { background:#111; color:#fff; border-color:#111; }

.hidden-btn {
  opacity: 0;
  transition: opacity 0.3s ease;
  margin-top: 20px;
}
.hidden-btn:hover {
  opacity: 1;
}

.hidden-text {
  color: transparent;
  user-select: text;
  transition: color 0.3s ease;
}
.hidden-text:hover {
  color: inherit;
}
.hidden-text::selection {
  background: rgba(0, 123, 255, 0.3);
  color: inherit;
}