.scroll-nav {
  position: fixed;
  right: max(12px, env(safe-area-inset-right));
  bottom: max(14px, calc(env(safe-area-inset-bottom) + 10px));
  z-index: 18;
  display: flex;
  flex-direction: column;
  gap: 8px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity .2s ease, transform .2s ease, visibility .2s;
}
.scroll-nav.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.scroll-nav button {
  width: 44px;
  height: 44px;
  border: 1px solid rgba(101, 215, 255, .65);
  border-radius: 50%;
  background: rgba(6, 22, 47, .92);
  color: #fff;
  box-shadow: 0 5px 18px rgba(6, 22, 47, .28);
  font: 800 1.12rem/1 sans-serif;
  cursor: pointer;
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
}
.scroll-nav button:active { transform: scale(.94); }
.scroll-nav button:focus-visible { outline: 3px solid #65d7ff; outline-offset: 2px; }
@media (min-width: 900px) {
  .scroll-nav { right: max(18px, calc((100vw - 1260px) / 2)); }
}
@media (prefers-reduced-motion: reduce) {
  .scroll-nav { transition: none; }
}