html, body { height: 100%; }
  * { box-sizing: border-box; }
  body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", Roboto, Helvetica, Arial, sans-serif;
    color: #1F2937;
    background: #EAF3FC;
    background-image: linear-gradient(180deg, #D9E9F7 0%, #EAF3FC 30%, #EAF3FC 100%);
    background-attachment: fixed;
    min-height: 100vh;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    margin: 0;
  }
  .app {
    position: relative;
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px 20px 56px;
    display: flex;
    flex-direction: column;
    gap: 18px;
  }
  a { text-decoration: none; color: inherit; }
  button { font-family: inherit; }

  /* ===== 导航栏 ===== */
  .nav-bar { background: #fff; box-shadow: 0 1px 4px rgba(0,0,0,0.05); }
  .nav {
    display: flex; align-items: center; gap: 24px;
    max-width: 1200px;
    margin: 0 auto;
    padding: 10px 20px;
  }
  .nav-logo { display: flex; align-items: center; gap: 8px; font-size: 18px; font-weight: 700; color: #1F2937; cursor: pointer; user-select: none; }
  .nav-logo svg { width: 24px; height: 24px; color: #0078D4; }
  .nav-menu { display: flex; align-items: center; gap: 6px; flex-wrap: wrap; }
  .nav-item {
    position: relative; display: flex; align-items: center; gap: 4px;
    padding: 7px 14px; border-radius: 999px;
    font-size: 14px; color: #374151; cursor: pointer; user-select: none;
    transition: background .2s, color .2s;
  }
  .nav-item:hover { background: #F3F4F6; color: #1F2937; }
  .nav-item.active { background: #E8F2FC; color: #0078D4; font-weight: 600; }
  .nav-item .caret { width: 12px; height: 12px; color: #9CA3AF; transition: transform .2s; }
  .nav-item.open .caret { transform: rotate(180deg); }
  .nav-drop-menu {
    position: absolute; top: calc(100% + 6px); left: 50%;
    transform: translateX(-50%) translateY(-4px);
    display: grid; grid-template-columns: repeat(2, 1fr); gap: 2px;
    min-width: 190px; background: #fff; border: 1px solid #E5E9F0;
    border-radius: 12px; box-shadow: 0 6px 18px rgba(0,0,0,0.08);
    padding: 6px; opacity: 0; visibility: hidden;
    transition: opacity .18s, transform .18s, visibility .18s; z-index: 60;
  }
  .nav-item.open .nav-drop-menu { opacity: 1; visibility: visible; transform: translateX(-50%) translateY(0); }
  .nav-drop-menu > div {
    padding: 8px 12px; font-size: 13px; color: #374151; border-radius: 8px;
    cursor: pointer; white-space: nowrap; transition: background .15s, color .15s;
  }
  .nav-drop-menu > div:hover { background: #F3F6FA; color: #0078D4; }

  /* ===== 面包屑 ===== */
  .crumb { font-size: 12.5px; color: #9CA3AF; }
  .crumb a:hover { color: #0078D4; }
  .crumb .sep { margin: 0 7px; color: #D1D5DB; }

  /* ===== 布局 ===== */
  .layout { display: grid; grid-template-columns: 1fr 320px; gap: 18px; align-items: start; }
  .main-col { display: flex; flex-direction: column; gap: 18px; min-width: 0; }
  .side-col { display: flex; flex-direction: column; gap: 18px; min-width: 0; }
  /* 桌面端侧栏吸顶跟随滚动；高度超过视口时改为贴底对齐，保证三张卡都能看到 */
  @media (min-width: 981px) {
    .side-col { position: sticky; top: 12px; }
  }

  .card { background: #fff; border: 1px solid #E5E9F0; border-radius: 14px; box-shadow: 0 1px 2px rgba(0,0,0,0.04); padding: 22px 24px; }
  .card > h2 { margin: 0 0 16px; font-size: 16px; font-weight: 600; color: #1F2937; display: flex; align-items: center; gap: 8px; }
  .card > h2 svg { width: 18px; height: 18px; color: #0078D4; }

  /* ===== 标签页 ===== */
  .tabs { display: flex; border-bottom: 2px solid #E5E9F0; overflow-x: auto; overflow-y: hidden; scrollbar-width: none; }
  .tabs::-webkit-scrollbar { display: none; width: 0; height: 0; }
  .tab {
    flex: 1 0 auto; min-width: 62px; text-align: center;
    padding: 13px 18px; line-height: 20px; font-size: 15.5px; color: #374151;
    cursor: pointer; user-select: none; white-space: nowrap;
    border-radius: 10px 10px 0 0; margin-bottom: -2px; transition: background .2s, color .2s;
  }
  .tab:hover { color: #0078D4; }
  .tab.active { background: #0078D4; color: #fff; font-weight: 600; }

  /* ===== AQI 主卡 ===== */
  .hero { display: flex; align-items: center; gap: 34px; padding: 8px 4px; }
  .aqi-circle {
    flex: 0 0 auto;
    width: 150px; height: 150px; border-radius: 50%;
    display: flex; flex-direction: column; align-items: center; justify-content: center;
    color: #fff; box-shadow: 0 4px 14px rgba(0,0,0,0.12);
  }
  .aqi-circle b { font-size: 46px; line-height: 1.1; font-variant-numeric: tabular-nums; }
  .aqi-circle span { font-size: 15px; font-weight: 600; margin-top: 2px; }
  .hero-info { min-width: 0; }
  .hero-info h1 { margin: 0 0 10px; font-size: 20px; font-weight: 700; color: #1F2937; }
  .hero-info .meta { font-size: 12.5px; color: #9CA3AF; margin-bottom: 10px; }
  .hero-info .meta b { color: #6B7280; font-weight: 600; }
  .hero-info .line { font-size: 13px; color: #4B5563; line-height: 1.9; }
  .hero-info .line b { color: #1F2937; }

  /* ===== 天气信息条 ===== */
  .weather-strip { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin-top: 18px; border-top: 1px dashed #E5E9F0; padding-top: 16px; }
  .wcell { text-align: center; }
  .wcell .wl { font-size: 12px; color: #9CA3AF; margin-bottom: 4px; }
  .wcell .wv { font-size: 15px; font-weight: 600; color: #1F2937; }
  .wcell .wv .wi { font-size: 16px; margin-right: 4px; }

  /* ===== 六项污染物 ===== */
  .polls { display: grid; grid-template-columns: repeat(6, 1fr); gap: 12px; }
  .poll {
    background: #fff; border: 1px solid #EDF0F5; border-top: 2px solid #BFD9F2;
    border-radius: 10px; text-align: center; padding: 14px 6px 12px;
    box-shadow: 0 1px 2px rgba(0,0,0,0.03);
  }
  .poll .pn { font-size: 13px; font-weight: 600; color: #374151; margin-bottom: 8px; }
  .poll .pv { font-size: 22px; font-weight: 700; color: #1F2937; font-variant-numeric: tabular-nums; }
  .poll .pv small { font-size: 11px; font-weight: 400; color: #9CA3AF; margin-left: 2px; }
  .poll .pd { font-size: 11px; color: #9CA3AF; margin-top: 6px; }

  /* ===== 预报表 ===== */
  .fc-head, .fc-row {
    display: grid; grid-template-columns: 1.2fr 1fr 1.5fr 1fr 1.3fr;
    align-items: center; padding: 10px 12px; text-align: center; font-size: 13.5px;
  }
  .fc-head { background: #F3F6FA; color: #6B7280; font-size: 12.5px; border-radius: 8px; }
  .fc-row { border-bottom: 1px solid #F5F7FA; }
  .fc-row:nth-child(even) { background: #FAFBFD; }
  .fc-row:last-child { border-bottom: none; }
  .fc-row .fw { color: #6B7280; }
  .fc-row .fw2 { color: #4B5563; font-size: 12.5px; }
  .fc-row .fa { font-weight: 700; color: #1F2937; font-variant-numeric: tabular-nums; }
  .lv-badge {
    display: inline-block; color: #fff; font-size: 12px; font-weight: 600;
    padding: 3px 12px; border-radius: 999px; white-space: nowrap;
  }

  /* ===== 等级说明表 ===== */
  .lvl-table { width: 100%; border-collapse: collapse; font-size: 12.5px; }
  .lvl-table th { background: #F3F6FA; color: #6B7280; font-weight: 600; padding: 10px 8px; text-align: left; }
  .lvl-table td { padding: 11px 8px; border-bottom: 1px solid #F5F7FA; color: #4B5563; line-height: 1.6; vertical-align: middle; }
  .lvl-table tr:last-child td { border-bottom: none; }
  .lvl-table .rng { font-weight: 700; color: #1F2937; white-space: nowrap; }

  /* ===== 空气导航 / SEO ===== */
  .navi { background: #EAF3FB; border: 1px solid #D8E8F6; border-radius: 14px; padding: 14px 20px; font-size: 13px; color: #4B5563; line-height: 2; }
  .navi b { color: #1F2937; }
  .navi a { color: #0078D4; margin-right: 14px; }
  .navi a:hover { text-decoration: underline; }
  .seo p { margin: 0; font-size: 13px; color: #6B7280; line-height: 1.9; }
  .seo h2 { font-size: 15px; }

  /* ===== 侧栏 ===== */
  .side-card { padding: 18px 18px 10px; }
  .side-card > h3 {
    margin: 0 0 12px; font-size: 14.5px; font-weight: 600; color: #1F2937;
    display: flex; align-items: center; gap: 7px; line-height: 20px;
    border-bottom: 2px solid #E8F0F8; padding-bottom: 8px;
  }
  .side-card > h3 svg { width: 15px; height: 15px; color: #0078D4; }
  .srow {
    display: flex; align-items: center; justify-content: space-between; gap: 10px;
    padding: 8px 2px; font-size: 13px; border-bottom: 1px solid #F7F9FC;
  }
  .srow:last-child { border-bottom: none; }
  .srow .sc { color: #374151; cursor: pointer; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
  .srow .sc:hover { color: #0078D4; }
  .srow .badge {
    display: inline-block; color: #fff; font-size: 11.5px; font-weight: 600;
    padding: 2px 8px; border-radius: 999px; white-space: nowrap; font-variant-numeric: tabular-nums;
  }
  .srow.wrow { grid-template-columns: 1fr auto; }
  .wrow2 { display: grid; grid-template-columns: 1fr 1fr auto; align-items: center; gap: 8px; }
  .wrow2 .wc { font-size: 13px; color: #374151; cursor: pointer; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
  .wrow2 .wc:hover { color: #0078D4; }
  .wrow2 .wcond { font-size: 12px; color: #6B7280; white-space: nowrap; }
  .wrow2 .wtemp { font-size: 14px; font-weight: 700; color: #FF8A00; font-variant-numeric: tabular-nums; }

  /* ===== 页脚 ===== */
  .foot { margin-top: 28px; border-top: 1px solid #EDF0F5; background: #fff; }
  .fl-wrap { max-width: 1200px; margin: 0 auto; padding: 0 20px; }
  .fl-row {
    display: flex; align-items: baseline; text-align: left;
    padding: 13px 0; font-size: 13px; border-bottom: 1px solid #F3F5F8;
  }
  .fl-label { color: #9CA3AF; flex-shrink: 0; }
  .fl-row a { margin-right: 26px; white-space: nowrap; }
  .fl-row a:last-child { margin-right: 0; }
  .fl-links a { color: #0078D4; text-decoration: none; }
  .fl-links a:hover { text-decoration: underline; }
  .nav-links a { color: #6B7280; }
  .nav-links a:hover { color: #0078D4; }
  .brand { padding: 16px 20px 20px; text-align: center; font-size: 12px; color: #6B7280; line-height: 1.9; }
  .brand svg { width: 15px; height: 15px; vertical-align: -2px; margin-right: 4px; color: #F59E0B; }
  .brand a { color: #0078D4; }
  .brand a:hover { text-decoration: underline; }
  .icp { color: #9CA3AF; }

  /* ===== 响应式 ===== */
  @media (max-width: 980px) {
    .layout { grid-template-columns: 1fr; }
  }
  @media (max-width: 720px) {
    .polls { grid-template-columns: repeat(3, 1fr); }
    .weather-strip { grid-template-columns: repeat(2, 1fr); }
    .fl-row { flex-wrap: wrap; row-gap: 6px; }
  }
  @media (max-width: 480px) {
    .app { padding: 14px 12px 40px; gap: 14px; }
    .card { padding: 16px 14px; border-radius: 12px; }
    .hero { flex-direction: column; gap: 16px; text-align: center; }
    .hero-info h1 { font-size: 17px; }
    .aqi-circle { width: 120px; height: 120px; }
    .aqi-circle b { font-size: 36px; }
    .polls { grid-template-columns: repeat(2, 1fr); }
    .tab { min-width: 52px; padding: 12px 0; line-height: 20px; font-size: 13.5px; }
    .fc-head, .fc-row { font-size: 12px; padding: 9px 6px; }
    .nav { gap: 14px; padding: 8px 12px; }
    .nav-logo { font-size: 16px; }
    .nav-item { padding: 6px 10px; font-size: 13px; }
    .nav-drop-menu { min-width: 160px; }
  }