.back-to-top {
  position: fixed; right: 1.25rem; bottom: 1.25rem; z-index: 90;
  width: 2.75rem; height: 2.75rem; padding: 0;
  display: flex; align-items: center; justify-content: center;
  background: #132238; color: #4a9eff;
  border: 1px solid rgba(74,158,255,0.45); border-radius: 50%;
  cursor: pointer; box-shadow: 0 4px 14px rgba(0,0,0,0.35);
  opacity: 0; visibility: hidden; transform: translateY(8px);
  transition: opacity .2s ease, transform .2s ease, visibility .2s, background .15s;
}
.back-to-top.visible { opacity: 1; visibility: visible; transform: none; }
.back-to-top:hover, .back-to-top:focus-visible { background: #1b3556; }
.back-to-top:focus-visible { outline: 2px solid #c8a96e; outline-offset: 2px; }
.back-to-top svg { width: 1.2rem; height: 1.2rem; }
@media (prefers-reduced-motion: reduce) { .back-to-top { transition: none; } }
@media print { .back-to-top { display: none; } }