/* ============================================
   Scroll to Top Button
   ============================================ */

.scroll-to-top {
  position: fixed;
  bottom: 80px;
  right: 20px;
  z-index: 98;

  /* Size - matching mobile TOC trigger */
  width: 44px;
  height: 44px;

  /* Appearance */
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--card);
  border: 1px solid var(--matrix-dim);
  border-radius: 50%;
  cursor: pointer;

  /* Initial state - hidden */
  opacity: 0;
  visibility: hidden;
  transform: translateY(20px);

  /* Transitions */
  transition:
    opacity 0.3s ease,
    visibility 0.3s ease,
    transform 0.3s ease,
    background-color 0.3s ease,
    border-color 0.3s ease,
    box-shadow 0.3s ease;
}

/* Visible state */
.scroll-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

/* Arrow icon */
.scroll-to-top svg {
  width: 20px;
  height: 20px;
  fill: none;
  stroke: var(--matrix-dim);
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
  transition: stroke 0.3s ease, transform 0.3s ease;
}

/* Hover state */
.scroll-to-top:hover {
  background: var(--matrix-dark);
  border-color: var(--matrix);
  box-shadow: var(--glow);
}

.scroll-to-top:hover svg {
  stroke: var(--matrix);
  transform: translateY(-2px);
}

/* Focus state for accessibility */
.scroll-to-top:focus {
  outline: none;
}

.scroll-to-top:focus-visible {
  outline: 2px solid var(--matrix);
  outline-offset: 2px;
  border-color: var(--matrix);
  box-shadow: var(--glow);
}

/* Active state */
.scroll-to-top:active {
  transform: scale(0.95);
}

.scroll-to-top:active svg {
  transform: translateY(-4px);
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
  .scroll-to-top {
    transition: opacity 0.1s ease, visibility 0.1s ease;
    transform: none;
  }

  .scroll-to-top.visible {
    transform: none;
  }

  .scroll-to-top svg {
    transition: none;
  }

  .scroll-to-top:hover svg,
  .scroll-to-top:active svg {
    transform: none;
  }
}

/* Mobile adjustments - move up when TOC trigger is present */
@media (max-width: 1100px) {
  .scroll-to-top {
    bottom: 80px; /* Above mobile TOC trigger at 20px */
  }
}

/* Larger screens - can be at bottom */
@media (min-width: 1101px) {
  .scroll-to-top {
    bottom: 30px;
  }
}