.site-back-to-top {
  position: fixed;
  z-index: 120;
  right: clamp(14px, 2.4vw, 34px);
  bottom: clamp(18px, 3.5vw, 42px);
  width: 54px;
  height: 54px;
  padding: 0;
  display: grid;
  place-items: center;
  color: #fff;
  border: 1px solid #0d2a47;
  border-radius: 50%;
  background: #0d2a47;
  box-shadow: inset 0 0 0 2px #faf5eb, 0 0 0 1px #0d2a47, 0 10px 28px rgb(13 42 71 / 24%);
  opacity: 0;
  pointer-events: none;
  transform: translateX(22px) scale(.82);
  transition: opacity 180ms ease, transform 180ms ease, background 160ms ease;
  cursor: pointer;
}

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

.site-back-to-top:hover { background: #183b5a; }
.site-back-to-top:focus-visible { outline: 3px solid #c57a24; outline-offset: 4px; }
.site-back-to-top svg { width: 27px; height: 27px; fill: none; stroke: currentColor; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; }

@media (max-width: 620px) {
  .site-back-to-top { right: 14px; bottom: 18px; width: 48px; height: 48px; }
  .site-back-to-top svg { width: 24px; height: 24px; }
}

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