/* 10. BACK TO TOP BUTTON - DARK THEME */
.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 60px;
  height: 60px;
  background: linear-gradient(135deg, #2c2c2c, #404040);
  border: 2px solid #06d5fadc;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0;
  /* visibility: hidden; */
  transform: translateY(20px);
  transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
  z-index: 2000;
  /* Dark theme box shadows */
  box-shadow: 0 8px 25px rgba(0, 0, 0, 0.6), 0 4px 10px rgba(0, 0, 0, 0.4),
    inset 0 1px 0 rgba(255, 255, 255, 0.1);
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  background: linear-gradient(135deg, #404040, #555);
  border-color: #666;
  transform: translateY(-3px);
  box-shadow: 0 12px 35px rgba(0, 0, 0, 0.7), 0 8px 15px rgba(0, 0, 0, 0.5),
    inset 0 1px 0 rgba(255, 255, 255, 0.15);
}

.back-to-top:active {
  transform: translateY(-1px);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.5), 0 3px 8px rgba(0, 0, 0, 0.3),
    inset 0 1px 0 rgba(255, 255, 255, 0.1);
}

/* Arrow icon */
.back-to-top::before {
  content: "";
  width: 0;
  height: 0;
  border-left: 8px solid transparent;
  border-right: 8px solid transparent;
  border-bottom: 12px solid #ffffff;
  filter: drop-shadow(0 1px 2px rgba(0, 0, 0, 0.3));
}

/* Mobile responsive for back to top button */
@media (max-width: 768px) {
  .back-to-top {
    bottom: 20px;
    right: 20px;
    width: 50px;
    height: 50px;
  }

  .back-to-top::before {
    border-left: 6px solid transparent;
    border-right: 6px solid transparent;
    border-bottom: 10px solid #ffffff;
  }
}