/* roulang page: index */
:root {
      --primary: hsl(215, 65%, 20%);
      --dark-bg: hsl(215, 45%, 11%);
      --accent: hsl(165, 82%, 39%);
      --accent-hover: hsl(165, 82%, 33%);
      --amber: hsl(38, 92%, 50%);
      --bg-surface: hsl(210, 20%, 98%);
      --text-main: hsl(215, 25%, 15%);
      --text-muted: hsl(215, 15%, 45%);
      --border-color: hsl(215, 15%, 88%);
    }
    html {
      scroll-behavior: smooth;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    }
    body {
      color: var(--text-main);
      background-color: var(--bg-surface);
      line-height: 1.75;
      overflow-x: hidden;
    }
    .custom-shadow {
      box-shadow: 0 1px 3px rgba(0,0,0,0.05), 0 20px 25px -5px rgba(15,23,42,0.04);
    }
    .hover-lift {
      transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    }
    .hover-lift:hover {
      transform: translateY(-4px);
      box-shadow: 0 12px 24px -6px rgba(15,23,42,0.12);
    }
    .tab-btn.active {
      background-color: var(--primary);
      color: #ffffff;
      border-color: var(--primary);
    }
    .tab-content {
      display: none;
    }
    .tab-content.active {
      display: block;
    }
    .accordion-content {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.35s ease-out;
    }
    .accordion-item.open .accordion-content {
      max-height: 320px;
    }
    .accordion-item.open .accordion-icon {
      transform: rotate(45deg);
    }
    #sticky-bar {
      transition: transform 0.3s ease, opacity 0.3s ease;
    }
    #sticky-bar.hidden-bar {
      transform: translateY(100%);
      opacity: 0;
      pointer-events: none;
    }