.back-to-top {
  position: fixed;
  z-index: 120;
  right: clamp(16px, 2vw, 28px);
  bottom: clamp(18px, 2vw, 28px);
  display: inline-flex;
  width: 54px;
  height: 54px;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--color-accent);
  border-radius: 0;
  background: var(--color-accent);
  color: var(--color-bg);
  box-shadow: var(--shadow-glow);
  opacity: 0;
  pointer-events: none;
  transform: translateY(14px);
  transition: opacity .2s ease, transform .2s ease, background .2s ease;
}

.back-to-top.is-visible {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
}

.back-to-top:hover {
  background: var(--color-accent-hover);
}

.back-to-top svg {
  width: 24px;
  height: 24px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

@media (max-width: 720px) {
  .back-to-top {
    right: 14px;
    bottom: calc(84px + env(safe-area-inset-bottom));
    width: 50px;
    height: 50px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .back-to-top { transition: none; }
}