.back-to-top {
  position: fixed;
  z-index: 80;
  right: 48px;
  bottom: 48px;
  width: 48px;
  height: 48px;
  padding: 0;
  border: 0;
  border-radius: 50%;
  background: transparent;
  box-shadow: 0 10px 28px rgba(0, 0, 0, .24);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translate3d(0, 12px, 0) scale(.92);
  transition: opacity .3s ease, visibility .3s ease, transform .45s cubic-bezier(.22, 1, .36, 1), filter .3s ease;
}

.site-copyright {
  position: relative;
  z-index: 2;
  isolation: isolate;
  overflow: hidden;
  width: 100%;
  min-height: 68px;
  padding: 0 max(48px, calc((100% - 1784px) / 2));
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 36px;
  color: rgba(255, 255, 255, .25);
  background: #01010b;
  font: 400 14px/14px "PingFang SC", "Helvetica Neue", Arial, sans-serif;
}

/* Global footer reference: keep every page identical to the Motion tab. */
html body .site-copyright--motion {
  color: rgba(255, 255, 255, .25);
  background-color: #01010b;
  border: 0;
  box-shadow: none;
  opacity: 1;
}

html body .site-copyright--motion::before {
  opacity: .055;
}

html body .site-copyright--motion p,
html body .site-copyright--motion .site-footer-nav,
html body .site-copyright--motion .site-footer-nav a {
  color: inherit;
  opacity: 1;
}

.site-copyright::before {
  content: "";
  position: absolute;
  z-index: -1;
  inset: 0;
  opacity: .055;
  pointer-events: none;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 180 180' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)' opacity='.75'/%3E%3C/svg%3E");
}

.site-copyright p { margin: 0; white-space: nowrap; }

.site-footer-nav {
  display: flex;
  align-items: center;
  gap: 36px;
  white-space: nowrap;
}

.site-footer-nav a {
  color: inherit;
  text-decoration: none;
  transition: color .25s ease;
}

.site-footer-nav a:hover { color: rgba(255,255,255,.72); }

.site-footer-nav span {
  width: 1px;
  height: 13px;
  background: rgba(255,255,255,.25);
}

.back-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translate3d(0, 0, 0) scale(1);
}

.back-to-top img {
  display: block;
  width: 48px;
  height: 48px;
}

.back-to-top:hover {
  filter: brightness(1.14) drop-shadow(0 0 12px rgba(83, 92, 255, .34));
  transform: translate3d(0, -3px, 0) scale(1.04);
}

.research-page .back-to-top:hover,
.materials-page .back-to-top:hover {
  filter: brightness(.97);
}

.research-page .back-to-top,
.materials-page .back-to-top {
  right: 37px;
  bottom: 37px;
  width: 69px;
  height: 69px;
  box-shadow: none;
}

.research-page .back-to-top img,
.materials-page .back-to-top img {
  width: 69px;
  height: 69px;
}

.back-to-top:focus-visible {
  outline: 2px solid #8f8fff;
  outline-offset: 4px;
}

@media (max-width: 900px) {
  .back-to-top {
    right: 20px;
    bottom: 20px;
  }
  .research-page .back-to-top,
  .materials-page .back-to-top {
    right: 10px;
    bottom: 10px;
  }
  .site-copyright { min-height: 112px; padding: 24px 20px; flex-direction: column; justify-content: center; gap: 18px; font-size: 10px; line-height: 14px; text-align:center; }
  .site-footer-nav { gap: 16px; font-size: 10px; }
}

@media (prefers-reduced-motion: reduce) {
  .back-to-top { transition: opacity .2s ease, visibility .2s ease; }
}