:root{
  --primary:#1a1a2e;--primary-light:#16213e;--accent:#e94560;--accent2:#0f3460;
  --gold:#f5a623;--green:#27ae60;--bg:#fafbfc;--card:#fff;
  --text:#1a1a2e;--muted:#6c757d;--border:#e9ecef;--radius:12px;
  --shadow:0 2px 16px rgba(0,0,0,.06);--shadow-lg:0 8px 32px rgba(0,0,0,.1);
}
*{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth}
body{font-family:'PingFang SC','Microsoft YaHei',-apple-system,'Segoe UI',sans-serif;background:var(--bg);color:var(--text);line-height:1.7;min-height:100vh}

/* NAV */
.topnav{position:fixed;top:0;left:0;right:0;z-index:1000;background:rgba(255,255,255,.95);backdrop-filter:blur(12px);border-bottom:1px solid var(--border);padding:0 24px;height:64px;display:flex;align-items:center;justify-content:space-between}
.topnav .logo{display:flex;align-items:center;gap:10px;text-decoration:none;font-weight:800;font-size:1.2rem;color:var(--primary)}
.topnav .logo span{background:linear-gradient(135deg,var(--accent),var(--gold));-webkit-background-clip:text;-webkit-text-fill-color:transparent}
.nav-links{display:flex;align-items:center;gap:6px}
.nav-links a{text-decoration:none;color:var(--muted);padding:8px 14px;border-radius:8px;font-size:.88rem;font-weight:500;transition:all .2s}
.nav-links a:hover,.nav-links a.active{color:var(--accent);background:rgba(233,69,96,.06)}
.nav-links .btn-accent{background:var(--accent);color:#fff;padding:8px 18px;border-radius:8px;font-weight:600}
.nav-links .btn-accent:hover{background:#d63851;color:#fff}
.nav-links .user-menu{display:flex;align-items:center;gap:8px;padding:6px 12px;border-radius:8px;background:#f8f9fa;cursor:pointer}
.nav-links .user-menu:hover{background:#e9ecef}
.nav-links .avatar{width:28px;height:28px;border-radius:50%;background:linear-gradient(135deg,var(--accent),var(--accent2));display:flex;align-items:center;justify-content:center;color:#fff;font-size:.75rem;font-weight:700}

/* HERO */
.hero{margin-top:64px;background:linear-gradient(135deg,var(--primary) 0%,var(--primary-light) 40%,var(--accent2) 100%);color:#fff;padding:80px 24px 72px;text-align:center;position:relative;overflow:hidden}
.hero::before{content:'';position:absolute;top:-100%;left:-100%;width:300%;height:300%;background:radial-gradient(ellipse at 30% 50%,rgba(233,69,96,.15) 0%,transparent 50%),radial-gradient(ellipse at 70% 50%,rgba(245,166,35,.1) 0%,transparent 50%);animation:heroGlow 12s ease-in-out infinite}
@keyframes heroGlow{0%,100%{transform:translate(0,0)}50%{transform:translate(5%,3%)}}
.hero h1{font-size:2.8rem;font-weight:800;margin-bottom:12px;position:relative;letter-spacing:-1px}
.hero h1 em{font-style:normal;color:var(--gold)}
.hero p{font-size:1.15rem;opacity:.85;max-width:600px;margin:0 auto 28px;position:relative}
.hero .cta{display:inline-flex;gap:12px;flex-wrap:wrap;justify-content:center;position:relative}
.hero .cta a{display:inline-block;padding:14px 32px;border-radius:10px;font-weight:700;font-size:1rem;text-decoration:none;transition:all .3s}
.hero .cta .primary{background:var(--accent);color:#fff;box-shadow:0 4px 20px rgba(233,69,96,.3)}
.hero .cta .primary:hover{transform:translateY(-2px);box-shadow:0 6px 24px rgba(233,69,96,.4)}
.hero .cta .secondary{background:rgba(255,255,255,.15);color:#fff;border:1px solid rgba(255,255,255,.3);backdrop-filter:blur(8px)}
.hero .cta .secondary:hover{background:rgba(255,255,255,.25)}

/* STATS */
.stats-bar{display:flex;justify-content:center;gap:48px;padding:24px;background:#fff;border-bottom:1px solid var(--border);flex-wrap:wrap}
.stat-item{text-align:center}
.stat-item .num{font-size:1.8rem;font-weight:800;color:var(--accent)}
.stat-item .label{font-size:.82rem;color:var(--muted);margin-top:2px}

/* SECTIONS */
.section{padding:64px 24px;max-width:1100px;margin:0 auto}
.section-title{font-size:1.6rem;font-weight:800;margin-bottom:8px}
.section-sub{color:var(--muted);margin-bottom:32px;font-size:.95rem}

/* COURSE GRID */
.course-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:20px}
.course-card{background:var(--card);border-radius:var(--radius);overflow:hidden;box-shadow:var(--shadow);border:1px solid var(--border);transition:all .3s;cursor:pointer}
.course-card:hover{transform:translateY(-4px);box-shadow:var(--shadow-lg);border-color:var(--accent)}
.course-card .thumb{height:160px;position:relative;overflow:hidden}
.course-card .thumb img{width:100%;height:100%;object-fit:cover}
.course-card .thumb .tag{position:absolute;top:12px;left:12px;padding:4px 10px;border-radius:6px;font-size:.72rem;font-weight:700;color:#fff}
.tag-beginner{background:var(--green)}.tag-intermediate{background:var(--gold)}.tag-advanced{background:var(--accent)}
.course-card .thumb .free{position:absolute;top:12px;right:12px;padding:4px 10px;border-radius:6px;font-size:.72rem;font-weight:700;background:#fff;color:var(--green)}
.course-card .info{padding:16px 20px}
.course-card .info h3{font-size:1.05rem;font-weight:700;margin-bottom:6px;line-height:1.4}
.course-card .info p{font-size:.85rem;color:var(--muted);line-height:1.6;margin-bottom:12px}
.course-card .meta{display:flex;align-items:center;justify-content:space-between;font-size:.78rem;color:var(--muted)}
.course-card .meta .lessons{display:flex;align-items:center;gap:4px}

/* FEATURES */
.features{display:grid;grid-template-columns:repeat(auto-fill,minmax(240px,1fr));gap:20px}
.feature-card{background:var(--card);border-radius:var(--radius);padding:28px 24px;box-shadow:var(--shadow);border:1px solid var(--border);text-align:center;transition:all .3s}
.feature-card:hover{border-color:var(--accent);transform:translateY(-2px)}
.feature-card .icon{font-size:2.4rem;margin-bottom:12px}
.feature-card h3{font-size:1rem;font-weight:700;margin-bottom:8px}
.feature-card p{font-size:.85rem;color:var(--muted);line-height:1.6}

/* PRICING */
.pricing{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:20px;max-width:920px;margin:0 auto}
.price-card{background:var(--card);border-radius:var(--radius);padding:32px 24px;box-shadow:var(--shadow);border:2px solid var(--border);text-align:center;transition:all .3s;position:relative}
.price-card.featured{border-color:var(--accent);box-shadow:var(--shadow-lg)}
.price-card.featured::before{content:'推荐';position:absolute;top:-12px;left:50%;transform:translateX(-50%);background:var(--accent);color:#fff;padding:2px 16px;border-radius:12px;font-size:.75rem;font-weight:700}
.price-card h3{font-size:1.1rem;font-weight:700;margin-bottom:4px}
.price-card .price{font-size:2.2rem;font-weight:800;color:var(--accent);margin:16px 0}
.price-card .price span{font-size:.9rem;color:var(--muted);font-weight:400}
.price-card ul{list-style:none;text-align:left;margin:20px 0}
.price-card ul li{padding:6px 0;font-size:.88rem;color:#4b5563;border-bottom:1px solid #f3f4f6}
.price-card ul li::before{content:'✓ ';color:var(--green);font-weight:700}
.price-card .btn{display:block;width:100%;padding:12px;border-radius:8px;font-weight:700;text-decoration:none;font-size:.95rem;transition:all .3s;margin-top:16px}
.price-card .btn-primary{background:var(--accent);color:#fff}
.price-card .btn-primary:hover{background:#d63851}
.price-card .btn-outline{border:2px solid var(--accent);color:var(--accent);background:transparent}
.price-card .btn-outline:hover{background:var(--accent);color:#fff}

/* FOOTER */
.footer{background:var(--primary);color:rgba(255,255,255,.7);padding:40px 24px;text-align:center;font-size:.85rem}
.footer a{color:var(--gold);text-decoration:none}
.footer .links{display:flex;justify-content:center;gap:24px;margin-bottom:16px;flex-wrap:wrap}
.footer .links a{color:rgba(255,255,255,.8)}

/* LOGIN FORM */
.auth-page{margin-top:64px;min-height:calc(100vh - 64px);display:flex;align-items:center;justify-content:center;background:linear-gradient(135deg,#f5f7fa 0%,#c3cfe2 100%);padding:40px 20px}
.auth-box{background:#fff;border-radius:16px;padding:40px;width:100%;max-width:420px;box-shadow:var(--shadow-lg)}
.auth-box h2{text-align:center;margin-bottom:8px;font-size:1.5rem}
.auth-box .subtitle{text-align:center;color:var(--muted);margin-bottom:28px;font-size:.9rem}
.auth-box .form-group{margin-bottom:16px}
.auth-box label{display:block;font-size:.85rem;font-weight:600;margin-bottom:6px;color:#374151}
.auth-box input{width:100%;padding:12px 14px;border:1px solid var(--border);border-radius:8px;font-size:.95rem;transition:all .2s}
.auth-box input:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px rgba(233,69,96,.1)}
.auth-box .btn-submit{width:100%;padding:14px;background:var(--accent);color:#fff;border:none;border-radius:8px;font-size:1rem;font-weight:700;cursor:pointer;transition:all .3s;margin-top:8px}
.auth-box .btn-submit:hover{background:#d63851}
.auth-box .switch{text-align:center;margin-top:20px;font-size:.85rem;color:var(--muted)}
.auth-box .switch a{color:var(--accent);text-decoration:none;font-weight:600}
.auth-box .error{color:var(--accent);font-size:.82rem;margin-top:8px;display:none}
.auth-box .tabs{display:flex;margin-bottom:24px;border-radius:8px;overflow:hidden;border:1px solid var(--border)}
.auth-box .tabs button{flex:1;padding:10px;border:none;background:#f8f9fa;cursor:pointer;font-weight:600;font-size:.9rem;transition:all .2s}
.auth-box .tabs button.active{background:var(--accent);color:#fff}

/* DASHBOARD */
.dash{margin-top:64px;display:flex;min-height:calc(100vh - 64px)}
.dash-sidebar{width:240px;background:#fff;border-right:1px solid var(--border);padding:24px 0;flex-shrink:0}
.dash-sidebar .profile{text-align:center;padding:0 20px 20px;border-bottom:1px solid var(--border);margin-bottom:16px}
.dash-sidebar .profile .avatar-lg{width:64px;height:64px;border-radius:50%;background:linear-gradient(135deg,var(--accent),var(--accent2));display:flex;align-items:center;justify-content:center;color:#fff;font-size:1.5rem;font-weight:700;margin:0 auto 10px}
.dash-sidebar .profile .name{font-weight:700;font-size:1rem}
.dash-sidebar .profile .tier{display:inline-block;padding:2px 10px;border-radius:10px;font-size:.72rem;font-weight:700;margin-top:4px}
.tier-free{background:#e8f5e9;color:var(--green)}.tier-pro{background:linear-gradient(135deg,#fff3e0,#fce4ec);color:var(--accent)}
.dash-sidebar nav a{display:flex;align-items:center;gap:10px;padding:10px 24px;text-decoration:none;color:var(--muted);font-size:.9rem;transition:all .2s}
.dash-sidebar nav a:hover,.dash-sidebar nav a.active{color:var(--accent);background:rgba(233,69,96,.05)}
.dash-main{flex:1;padding:32px;background:#f8f9fa;overflow-y:auto}
.dash-main h2{font-size:1.3rem;font-weight:800;margin-bottom:20px}

/* MY COURSES */
.my-course{background:#fff;border-radius:var(--radius);padding:20px;box-shadow:var(--shadow);border:1px solid var(--border);margin-bottom:16px;display:flex;gap:16px;align-items:center;transition:all .2s}
.my-course:hover{border-color:var(--accent)}
.my-course .thumb-sm{width:120px;height:80px;border-radius:8px;overflow:hidden;flex-shrink:0}
.my-course .thumb-sm img{width:100%;height:100%;object-fit:cover}
.my-course .info{flex:1}
.my-course .info h4{font-size:.95rem;font-weight:700;margin-bottom:4px}
.my-course .info p{font-size:.82rem;color:var(--muted)}
.my-course .progress{width:120px}
.my-course .progress-bar{height:6px;background:#e9ecef;border-radius:3px;overflow:hidden}
.my-course .progress-fill{height:100%;background:var(--green);border-radius:3px}
.my-course .progress-text{font-size:.72rem;color:var(--muted);margin-top:4px;text-align:right}

/* ALERTS */
.toast{position:fixed;top:80px;right:24px;padding:14px 20px;border-radius:10px;font-size:.9rem;font-weight:600;color:#fff;z-index:9999;transform:translateX(120%);transition:transform .4s ease;box-shadow:var(--shadow-lg)}
.toast.show{transform:translateX(0)}
.toast-success{background:var(--green)}.toast-error{background:var(--accent)}

/* RESPONSIVE */
@media(max-width:768px){
  .hero h1{font-size:1.8rem}
  .hero p{font-size:1rem}
  .stats-bar{gap:24px;padding:16px}
  .stat-item .num{font-size:1.3rem}
  .course-grid{grid-template-columns:1fr}
  .pricing{grid-template-columns:1fr}
  .features{grid-template-columns:1fr 1fr}
  .dash{flex-direction:column}
  .dash-sidebar{width:100%;border-right:none;border-bottom:1px solid var(--border);padding:16px 0}
  .dash-sidebar nav{display:flex;overflow-x:auto;padding:0 16px;gap:4px}
  .dash-sidebar nav a{white-space:nowrap;padding:8px 12px;border-radius:8px}
  .nav-links a:not(.btn-accent):not(.user-menu){display:none}
  .my-course{flex-direction:column;align-items:stretch}
  .my-course .thumb-sm{width:100%;height:120px}
}