:root{
    --bg:#ffffff;
    --fg:#0a0a0a;
    --muted:#6b7280;
    --line:#e5e7eb;
    --card:#ffffff;
    --alt:#f7f7f8;
    --shadow: 0 10px 30px rgba(0,0,0,.08);
    --radius: 20px;
  }
  
  *{ box-sizing:border-box; }
  html{ scroll-behavior:smooth; overflow-x:hidden; }
  body{
    margin:0;
    min-width:0;
    overflow-x:hidden;
    font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji","Segoe UI Emoji";
    color:var(--fg);
    background:var(--bg);
  }

  a{ color:inherit; text-decoration:none; }
  img{ max-width:100%; height:auto; display:block; }
  main{ min-width:0; }

  .container{
    width:100%;
    max-width:1100px;
    margin:0 auto;
    padding-left:max(24px, env(safe-area-inset-left));
    padding-right:max(24px, env(safe-area-inset-right));
  }
  @media (max-width: 480px){
    .container{ padding-left:max(16px, env(safe-area-inset-left)); padding-right:max(16px, env(safe-area-inset-right)); }
  }
  
  /* Header */
  .header{
    position:fixed; 
    top:0; 
    left:0;
    right:0;
    z-index:50;
    background: rgba(255,255,255,.85);
    backdrop-filter: blur(12px);
    border-bottom:1px solid var(--line);
  }
  
  /* 为 body 添加顶部内边距，避免内容被固定导航栏遮挡 */
  body{
    padding-top: 70px;
  }
  .header__inner{
    display:flex; align-items:center; justify-content:space-between;
    padding:16px 0;
  }
  .brand{ display:flex; gap:12px; align-items:center; min-width:0; }
  .brand__logo{ width:38px; height:38px; min-width:38px; border-radius:14px; background:#111; }
  .brand__text{ display:flex; flex-direction:column; line-height:1.1; min-width:0; }
  .brand__text strong{ overflow-wrap:break-word; word-break:break-word; }
  .brand__text small{ color:var(--muted); font-size:12px; margin-top:3px; }
  
  .nav{ display:flex; gap:18px; align-items:center; }
  .nav a{ font-size:14px; color:#111; opacity:.85; }
  .nav a:hover{ opacity:1; }
  .nav__toggle{
    display:none;
    border:1px solid var(--line);
    background:#fff;
    padding:8px 12px;
    border-radius:14px;
    font-size:14px;
  }
  
  /* Buttons */
  .btn{
    display:inline-flex; align-items:center; justify-content:center;
    padding:10px 16px;
    border-radius:16px;
    font-size:14px;
    border:1px solid var(--line);
    background:#fff;
  }
  .btn.btn--primary{
    background:#111;
    color:#fff;
    border-color:#111;
  }
  .btn--primary:hover{ opacity:.92; }
  .btn--ghost:hover{ background:#f3f4f6; }
  
/* Hero */
  .hero{
    position:relative;
    overflow:hidden;
    padding:clamp(32px, 8vw, 72px) 0 clamp(20px, 4vw, 30px);
  }
  .hero::before{
    content:"";
    position:absolute; inset:0;
    background:
      radial-gradient(circle at 20% 20%, rgba(0,0,0,.08), transparent 45%),
      radial-gradient(circle at 80% 40%, rgba(0,0,0,.06), transparent 40%);
    pointer-events:none;
  }
  .hero__inner{
    position:relative;
    display:grid;
    grid-template-columns: 1.15fr .85fr;
    gap:clamp(24px, 4vw, 36px);
    align-items:center;
  }
  .pill{
    display:inline-block;
    border:1px solid var(--line);
    background:#fff;
    padding:6px 10px;
    border-radius:999px;
    font-size:12px;
    color:#111;
  }
  .hero h1{
    margin:14px 0 0;
    font-size:clamp(26px, 5vw, 46px);
    letter-spacing:-.02em;
    line-height:1.2;
  }
  .muted{ color:var(--muted); }
  .small{ font-size:12px; }

  .hero__actions{ margin-top:18px; display:flex; gap:12px; flex-wrap:wrap; }

  .stats{
    margin-top:18px;
    display:grid;
    grid-template-columns: repeat(3, 1fr);
    gap:12px;
  }
  .stat{
    border:1px solid var(--line);
    background:#fff;
    border-radius:18px;
    padding:12px 14px;
  }
  .stat__k{ font-size:18px; font-weight:700; }
  .stat__v{ font-size:12px; color:var(--muted); margin-top:4px; }
  
  .hero__card .card{
    border:1px solid var(--line);
    border-radius:28px;
    background:var(--card);
    box-shadow: var(--shadow);
    padding:18px;
  }
  .card__title{ font-weight:700; font-size:18px; margin:6px 0 14px; }
  .grid2{ display:grid; grid-template-columns: repeat(2, 1fr); gap:10px; }
  .mini{
    border-radius:18px;
    background:#111;
    color:#fff;
    padding:12px;
  }
  .mini__t{ font-size:12px; opacity:.75; }
  .mini__v{ font-size:20px; font-weight:700; margin-top:6px; }
  .card__note{ margin-top:14px; font-size:13px; }
  
  /* Sections */
  .section{ padding:clamp(32px, 8vw, 56px) 0; }
  .section--alt{ background:var(--alt); border-top:1px solid var(--line); border-bottom:1px solid var(--line); }
  .section h2{ margin:0; font-size:clamp(22px, 4vw, 28px); letter-spacing:-.01em; }
  .section p{ margin:10px 0 0; }
  
  .panel{
    border:1px solid var(--line);
    background:#fff;
    border-radius:var(--radius);
    padding:18px;
    box-shadow: 0 1px 0 rgba(0,0,0,.02);
  }
  .panel h3{ margin:0 0 10px; font-size:16px; }
  .cards3{ margin-top:18px; display:grid; grid-template-columns: repeat(3, 1fr); gap:14px; }
  .cards2{ margin-top:18px; display:grid; grid-template-columns: repeat(2, 1fr); gap:14px; }
  
  /* Channels */
  .channel-groups {
    margin-top: 24px;
    display: flex;
    flex-wrap: wrap;
    gap: 28px 40px;
  }
  
  .channel-group {
    min-width: 0;
  }
  
  .channel-group__title {
    font-size: 14px;
    font-weight: 600;
    color: var(--muted);
    text-transform: uppercase;
    letter-spacing: 0.04em;
    margin: 0 0 12px 0;
  }
  
  .channel-group .channels {
    margin-top: 0;
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
  }
  
  .channels {
    margin-top: 24px;
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
  }
  
  .channel-item {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 24px;
    background: #fff;
    border: 1px solid var(--line);
    border-radius: 999px;
    font-size: 15px;
    font-weight: 500;
    color: var(--fg);
    transition: all 0.2s ease;
    box-shadow: 0 1px 2px rgba(0,0,0,0.05);
    cursor: pointer;
  }
  
  .channel-item:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
    border-color: #111;
  }

  /* 培训课程 */
  .course-grid{
    margin-top:18px;
    display:grid;
    grid-template-columns: repeat(3, 1fr);
    gap:20px;
  }
  .course-card{
    min-width:0;
    border:1px solid var(--line);
    background:#fff;
    border-radius:var(--radius);
    overflow:hidden;
    box-shadow: 0 1px 0 rgba(0,0,0,.02);
    transition: box-shadow .2s, transform .2s;
  }
  .course-card:hover{
    box-shadow: var(--shadow);
    transform: translateY(-2px);
  }
  .course-card__link{
    display:block;
    color:inherit;
  }
  .course-card__img{
    width:100%;
    aspect-ratio: 1587/2245;
    object-fit:contain;
    object-position:center;
    vertical-align:middle;
    background:var(--alt);
  }
  .course-card__title{
    display:block;
    padding:14px 18px;
    font-size:15px;
    font-weight:600;
    line-height:1.35;
    overflow-wrap:break-word;
    word-break:break-word;
  }

  /* 学术讨论（B 站视频） */
  .video-grid{
    margin-top:18px;
    display:grid;
    grid-template-columns: repeat(2, 1fr);
    gap:20px;
  }
  .video-card{
    min-width:0;
    border:1px solid var(--line);
    background:#fff;
    border-radius:var(--radius);
    overflow:hidden;
    box-shadow: 0 1px 0 rgba(0,0,0,.02);
    transition: box-shadow .2s, transform .2s;
  }
  .video-card:hover{
    box-shadow: var(--shadow);
    transform: translateY(-2px);
  }
  .video-card__link{
    display:flex;
    flex-direction:column;
    padding:0;
    color:inherit;
    min-height:140px;
  }
  .video-card__thumb{
    display:block;
    aspect-ratio: 16/9;
    overflow:hidden;
    background:var(--alt);
  }
  .video-card__thumb img{
    width:100%;
    height:100%;
    object-fit:contain;
    vertical-align:middle;
  }
  .video-card__title{
    display:block;
    padding:12px 18px 6px;
    font-size:15px;
    font-weight:600;
    line-height:1.35;
    overflow-wrap:break-word;
    word-break:break-word;
  }
  .video-card__action{
    display:block;
    padding:0 18px 14px;
    font-size:13px;
    color:var(--muted);
  }
  .video-card__link:hover .video-card__action{ color:#111; }

  /* 技术博客 */
  .blog-grid{
    display:grid;
    grid-template-columns: repeat(3, 1fr);
    gap:20px;
  }
  .blog-card{
    position:relative;
    min-width:0;
    border:1px solid var(--line);
    background:#fff;
    border-radius:var(--radius);
    padding:20px;
    box-shadow: 0 1px 0 rgba(0,0,0,.02);
    transition: box-shadow .2s, transform .2s, border-color .2s;
  }
  .blog-card:hover{
    box-shadow: var(--shadow);
    transform: translateY(-2px);
    border-color:#111;
  }
  .blog-card__link{
    display:block;
    color:inherit;
  }
  .blog-card__badge{
    display:inline-block;
    background:#111;
    color:#fff;
    font-size:11px;
    font-weight:600;
    padding:4px 10px;
    border-radius:999px;
    text-transform:uppercase;
    letter-spacing:0.03em;
    margin-bottom:12px;
  }
  .blog-card__title{
    font-size:18px;
    font-weight:700;
    line-height:1.3;
    margin:0 0 10px;
    overflow-wrap:break-word;
    word-break:break-word;
  }
  .blog-card__desc{
    font-size:14px;
    line-height:1.6;
    color:var(--muted);
    margin:0 0 14px;
    overflow-wrap:break-word;
    word-break:break-word;
  }
  .blog-card__meta{
    display:flex;
    gap:8px;
    flex-wrap:wrap;
  }
  .blog-card__tag{
    display:inline-block;
    font-size:12px;
    color:var(--muted);
    background:var(--alt);
    padding:4px 10px;
    border-radius:999px;
  }

  /* 分类卡片 */
  .category-grid{
    display:grid;
    grid-template-columns: repeat(4, 1fr);
    gap:16px;
  }
  .category-card{
    min-width:0;
    border:1px solid var(--line);
    background:#fff;
    border-radius:18px;
    padding:18px;
    text-align:center;
    box-shadow: 0 1px 0 rgba(0,0,0,.02);
    transition: box-shadow .2s, transform .2s, border-color .2s;
  }
  .category-card:hover{
    box-shadow: var(--shadow);
    transform: translateY(-2px);
    border-color:#111;
  }
  .category-card__link{
    display:block;
    color:inherit;
  }
  .category-card__icon{
    font-size:32px;
    margin-bottom:10px;
  }
  .category-card__title{
    font-size:15px;
    font-weight:600;
    margin:0 0 6px;
    overflow-wrap:break-word;
    word-break:break-word;
  }
  .category-card__desc{
    font-size:13px;
    color:var(--muted);
    margin:0;
    overflow-wrap:break-word;
    word-break:break-word;
  }

  /* 团队成员卡片 */
  .team-grid{
    display:grid;
    grid-template-columns: repeat(2, 1fr);
    gap:24px;
  }
  .team-card{
    border:1px solid var(--line);
    background:#fff;
    border-radius:var(--radius);
    padding:24px;
    box-shadow: 0 1px 0 rgba(0,0,0,.02);
    transition: box-shadow .2s, transform .2s;
  }
  .team-card:hover{
    box-shadow: var(--shadow);
    transform: translateY(-2px);
  }
  .team-card__header{
    display:flex;
    gap:16px;
    align-items:center;
    padding-bottom:20px;
    border-bottom:1px solid var(--line);
  }
  .team-card__avatar{
    width:80px;
    height:80px;
    min-width:80px;
    border-radius:50%;
    overflow:hidden;
    background:var(--alt);
    border:2px solid var(--line);
  }
  .team-card__avatar img{
    width:100%;
    height:100%;
    object-fit:cover;
  }
  .team-card__info{
    min-width:0;
  }
  .team-card__name{
    font-size:20px;
    font-weight:700;
    margin:0 0 6px;
    overflow-wrap:break-word;
    word-break:break-word;
  }
  .team-card__title{
    font-size:14px;
    color:var(--muted);
    margin:0;
    overflow-wrap:break-word;
    word-break:break-word;
  }
  .team-card__content{
    margin-top:20px;
  }
  .team-card__section{
    margin-bottom:20px;
  }
  .team-card__section:last-child{
    margin-bottom:0;
  }
  .team-card__section h5{
    font-size:15px;
    font-weight:600;
    margin:0 0 10px;
  }
  .team-card__section p{
    font-size:14px;
    line-height:1.6;
    color:var(--muted);
    margin:0;
    overflow-wrap:break-word;
    word-break:break-word;
  }
  .team-card__contact{
    display:flex;
    flex-direction:column;
    gap:10px;
  }
  .contact-item{
    display:flex;
    align-items:center;
    gap:10px;
    font-size:14px;
    color:var(--muted);
    padding:8px 12px;
    background:var(--alt);
    border-radius:12px;
  }
  .contact-icon{
    font-size:18px;
  }
  
  /* 占位卡片 */
  .team-card--placeholder{
    display:flex;
    align-items:center;
    justify-content:center;
    min-height:400px;
    background:var(--alt);
    border-style:dashed;
  }
  .team-card__placeholder-content{
    text-align:center;
    padding:20px;
  }
  .team-card__placeholder-icon{
    font-size:48px;
    margin-bottom:16px;
    opacity:0.5;
  }
  .team-card__placeholder-content h4{
    font-size:18px;
    font-weight:600;
    margin:0 0 10px;
  }
  .team-card__placeholder-content p{
    font-size:14px;
    color:var(--muted);
    margin:0;
    max-width:280px;
    margin-left:auto;
    margin-right:auto;
  }

  /* 课程详情页 */
  .course-detail__back{
    display:inline-block;
    margin-bottom:16px;
    font-size:14px;
  }
  .course-detail__back:hover{ color:#111; }
  .course-detail__title{ margin:0; font-size:32px; letter-spacing:-.02em; line-height:1.2; }
  .course-detail__subtitle{ margin:8px 0 0; font-size:16px; }
  .course-detail__cover{
    margin-top:24px;
    border-radius:var(--radius);
    overflow:hidden;
    border:1px solid var(--line);
    background:var(--alt);
  }
  .course-detail__img{
    width:100%;
    display:block;
    vertical-align:middle;
  }
  .course-detail__content{
    margin-top:32px;
    max-width:720px;
  }
  .course-detail__content h2{
    margin:24px 0 12px;
    font-size:20px;
    font-weight:600;
  }
  .course-detail__content h2:first-child{ margin-top:0; }
  .course-detail__content p{ margin:0 0 12px; line-height:1.6; }
  .course-detail__content .list{ margin:0 0 12px; }
  .course-detail__cta{ margin-top:28px; }
  
  .list{ margin:10px 0 0; padding-left:18px; color:#111; }
  .list li{ margin:6px 0; color:#111; }
  .list li::marker{ color:#111; }
  
  .pricing{
    margin-top:18px;
    display:grid;
    grid-template-columns: repeat(3, 1fr);
    gap:14px;
  }
  .price{
    position:relative;
    border:1px solid var(--line);
    background:#fff;
    border-radius:var(--radius);
    padding:18px;
  }
  .price__n{ font-size:34px; font-weight:800; margin:10px 0; letter-spacing:-.02em; }
  .price--hot{ border-color:#111; box-shadow: var(--shadow); }
  .badge{
    position:absolute; top:14px; right:14px;
    background:#111; color:#fff;
    font-size:12px;
    padding:6px 10px;
    border-radius:999px;
  }
  
  .contact{
    margin-top:18px;
    display:grid;
    grid-template-columns: 1fr 1fr;
    gap:14px;
  }
  label{ display:grid; gap:8px; margin-top:12px; }
  input, textarea{
    width:100%;
    border:1px solid var(--line);
    border-radius:16px;
    padding:12px 14px;
    font-size:14px;
    outline:none;
  }
  input:focus, textarea:focus{ border-color:#9ca3af; }
  .hint{
    margin-top:14px;
    border-radius:16px;
    padding:12px 14px;
    background:#f3f4f6;
    color:var(--muted);
    font-size:13px;
  }
  
  /* Footer */
  .footer{
    border-top:1px solid var(--line);
    padding:26px 0;
  }
  .footer__inner{
    display:flex; align-items:center; justify-content:space-between;
    gap:14px;
    flex-wrap:wrap;
  }
  .footer__links{ display:flex; gap:14px; flex-wrap:wrap; }
  .footer__links a{ font-size:14px; color:var(--muted); }
  .footer__links a:hover{ color:#111; }
  .footer__icp{ margin:12px 0 0; font-size:13px; }
  .footer__icp a{ color:var(--muted); }
  .footer__icp a:hover{ color:#111; }
  
/* Responsive */
  @media (max-width: 920px){
    .hero__inner{ grid-template-columns: 1fr; text-align:center; }
    .hero__actions{ justify-content:center; }
    .stats{ justify-content:center; max-width:360px; margin-left:auto; margin-right:auto; }
    .course-grid{ grid-template-columns: repeat(2, 1fr); }
    .video-grid{ grid-template-columns: repeat(2, 1fr); }
    .blog-grid{ grid-template-columns: repeat(2, 1fr); }
    .category-grid{ grid-template-columns: repeat(2, 1fr); }
    .team-grid{ grid-template-columns: 1fr; }
    .channel-groups{ justify-content:center; }
  }

  @media (max-width: 760px){
    .header__inner{ padding:12px 0; }
    .brand__text small{ display:none; }
    .nav__toggle{ display:inline-flex; }
    .nav{
      display:none;
      position:absolute;
      right:24px; top:60px;
      flex-direction:column;
      background:#fff;
      border:1px solid var(--line);
      border-radius:18px;
      padding:12px;
      gap:10px;
      width:min(280px, calc(100vw - 48px));
      box-shadow: var(--shadow);
    }
    .nav.is-open{ display:flex; }
    .cards3{ grid-template-columns: 1fr; }
    .cards2{ grid-template-columns: 1fr; }
    .course-grid{ grid-template-columns: 1fr; }
    .video-grid{ grid-template-columns: 1fr; }
    .blog-grid{ grid-template-columns: 1fr; }
    .category-grid{ grid-template-columns: 1fr; }
    .team-grid{ grid-template-columns: 1fr; }
    .pricing{ grid-template-columns: 1fr; }
    .contact{ grid-template-columns: 1fr; }
    .stats{ grid-template-columns: 1fr; max-width:none; }
    .hero__inner{ text-align:left; }
    .hero__actions{ justify-content:flex-start; }
    .channel-groups{ justify-content:flex-start; }
    .footer__inner{ flex-direction:column; align-items:flex-start; }
    .hero__card .grid2{ grid-template-columns: 1fr; }
  }

  @media (max-width: 480px){
    .hero h1{ font-size:26px; }
    .section h2{ font-size:22px; }
    .stat__k{ font-size:16px; }
    .course-detail__title{ font-size:24px; }
    .price__n{ font-size:28px; }
    .channel-item{ padding:10px 18px; font-size:14px; }
    .blog-card__title{ font-size:16px; }
    .category-card__icon{ font-size:28px; }
    .team-card{ padding:18px; }
    .team-card__avatar{ width:60px; height:60px; min-width:60px; }
    .team-card__name{ font-size:18px; }
  }
  

  /* 悬浮按钮：更多内容 */
  .floating-shop-btn {
    position: fixed;
    bottom: 24px;
    right: 24px;
    z-index: 100;
  }

  .floating-shop-btn__trigger {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 14px 20px;
    background: #111;
    color: #fff;
    border: none;
    border-radius: 999px;
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    box-shadow: 0 4px 20px rgba(0,0,0,0.15);
    transition: all 0.3s ease;
  }

  .floating-shop-btn__trigger:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 24px rgba(0,0,0,0.2);
  }

  .floating-shop-btn__trigger svg {
    width: 20px;
    height: 20px;
  }

  .floating-shop-btn__menu {
    position: absolute;
    bottom: 70px;
    right: 0;
    width: 280px;
    background: #fff;
    border: 1px solid var(--line);
    border-radius: 18px;
    box-shadow: 0 8px 32px rgba(0,0,0,0.12);
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: all 0.3s ease;
  }

  .floating-shop-btn__menu.is-open {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
  }

  .floating-shop-btn__menu-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 18px;
    border-bottom: 1px solid var(--line);
  }

  .floating-shop-btn__menu-header h4 {
    margin: 0;
    font-size: 16px;
    font-weight: 600;
  }

  .floating-shop-btn__close {
    width: 28px;
    height: 28px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--alt);
    border: none;
    border-radius: 50%;
    font-size: 20px;
    color: var(--muted);
    cursor: pointer;
    transition: all 0.2s ease;
  }

  .floating-shop-btn__close:hover {
    background: var(--line);
    color: #111;
  }

  .floating-shop-btn__menu-content {
    padding: 12px;
  }

  .floating-shop-btn__link {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 16px;
    border-radius: 12px;
    transition: all 0.2s ease;
    margin-bottom: 8px;
  }

  .floating-shop-btn__link:last-child {
    margin-bottom: 0;
  }

  .floating-shop-btn__link:hover {
    background: var(--alt);
  }

  .floating-shop-btn__icon {
    font-size: 24px;
    min-width: 24px;
  }

  .floating-shop-btn__text {
    font-size: 15px;
    font-weight: 500;
    color: #111;
  }

  /* 响应式 */
  @media (max-width: 480px) {
    .floating-shop-btn {
      bottom: 16px;
      right: 16px;
    }

    .floating-shop-btn__trigger {
      padding: 12px 16px;
      font-size: 14px;
    }

    .floating-shop-btn__trigger span {
      display: none;
    }

    .floating-shop-btn__menu {
      width: calc(100vw - 32px);
      right: -16px;
    }
  }