html { scroll-behavior: smooth; }
  #backToTop {
    position: fixed;
    right: 24px;
    bottom: 24px;
    width: 44px;
    height: 44px;
    border: none;
    border-radius: 50%;
    background: rgba(0,0,0,0.6);
    color: #fff;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    pointer-events: none;
    transform: translateY(8px);
    transition: opacity .25s ease, transform .25s ease;
    z-index: 1000;
  }
  #backToTop.show {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
  }
  #backToTop:focus-visible { outline: 2px solid #ffffff; outline-offset: 2px; }
  #backToTop svg { width: 22px; height: 22px; }