/**
 * Module CSS: 11-back-to-top.css
 * Trích nguyên văn dòng 478-498 của pctech-homepage.css gốc.
 * Không đổi nội dung — chỉ tách file theo đúng marker sẵn có trong code gốc.
 */
    /* ── Back to top ── */
    .back-to-top {
      position: fixed;
      right: 28px;
      bottom: 220px;
      width: 48px; height: 48px;
      border-radius: 50%;
      background: var(--orange);
      color: var(--white);
      border: none;
      cursor: pointer;
      font-size: 1.5rem;
      font-weight: 900;
      line-height: 1;
      display: flex;
      align-items: center;
      justify-content: center;
      box-shadow: 0 4px 16px rgba(245,158,11,0.4);
      opacity: 0;
      transform: translateY(20px);
      transition: opacity 0.3s, transform 0.3s;
      z-index: 999;
    }
    .back-to-top.visible { opacity: 1; transform: translateY(0); }
    .back-to-top:hover { transform: translateY(-4px); }