/* ============ 设计令牌 ============ */
:root{
  --brand:#12b886; --brand-2:#0ca678; --brand-ink:#087f5b;
  --accent:#4c6ef5; --accent-2:#7950f2; --gold:#f59f00; --danger:#e03131;

  --bg:#f6f8fb; --bg-2:#eef2f7; --card:#ffffff; --card-2:#fbfcfe;
  --ink:#101828; --ink-2:#344054; --muted:#667085; --line:#e6ebf1;
  --shadow-sm:0 1px 2px rgba(16,24,40,.05);
  --shadow:0 4px 6px -2px rgba(16,24,40,.04), 0 12px 24px -6px rgba(16,24,40,.10);
  --shadow-lg:0 18px 44px -12px rgba(16,24,40,.22);
  --glow:0 0 0 1px rgba(18,184,134,.18), 0 10px 34px -8px rgba(18,184,134,.35);
  --radius:16px; --radius-sm:10px; --radius-lg:24px;
  --maxw:1160px;
}
:root[data-theme="dark"]{
  --bg:#0b1120; --bg-2:#0f1729; --card:#131c2f; --card-2:#182238;
  --ink:#f2f6fc; --ink-2:#cbd5e1; --muted:#94a3b8; --line:#233047;
  --shadow-sm:0 1px 2px rgba(0,0,0,.4);
  --shadow:0 4px 8px -2px rgba(0,0,0,.4), 0 16px 32px -8px rgba(0,0,0,.5);
  --shadow-lg:0 22px 50px -14px rgba(0,0,0,.7);
  --glow:0 0 0 1px rgba(18,184,134,.3), 0 10px 40px -8px rgba(18,184,134,.45);
}

*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0; background:var(--bg); color:var(--ink);
  font:16px/1.7 -apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;
  -webkit-font-smoothing:antialiased;
  background-image:
    radial-gradient(60rem 30rem at 12% -8%, rgba(18,184,134,.10), transparent 60%),
    radial-gradient(48rem 26rem at 92% 4%, rgba(76,110,245,.10), transparent 60%);
}
a{color:inherit;text-decoration:none}
h1,h2,h3{line-height:1.25;margin:0 0 .5em;letter-spacing:-.02em}
h1{font-size:clamp(28px,4vw,40px);font-weight:800}
h2{font-size:clamp(20px,2.4vw,26px);font-weight:700}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 22px}
.muted{color:var(--muted)}
.pad{padding:18px}
.pad-xl{padding:64px}
.center{text-align:center}
.spacer{flex:1}
.inline{display:inline}

/* ============ 顶栏 ============ */
.topbar{
  position:sticky;top:0;z-index:30;
  background:color-mix(in srgb, var(--card) 82%, transparent);
  backdrop-filter:saturate(180%) blur(14px);
  -webkit-backdrop-filter:saturate(180%) blur(14px);
  border-bottom:1px solid var(--line);
}
.topbar-inner{display:flex;align-items:center;justify-content:space-between;height:66px;gap:16px}
.brand{
  font-weight:800;font-size:20px;letter-spacing:-.03em;
  background:linear-gradient(100deg,var(--brand),var(--accent));
  -webkit-background-clip:text;background-clip:text;color:transparent;
}
.nav{display:flex;align-items:center;gap:16px;flex-wrap:wrap}
.nav a{color:var(--muted);font-size:15px;font-weight:500;position:relative;padding:4px 0;transition:color .18s}
.nav a:not(.btn):after{
  content:'';position:absolute;left:0;right:0;bottom:0;height:2px;border-radius:2px;
  background:linear-gradient(90deg,var(--brand),var(--accent));
  transform:scaleX(0);transform-origin:left;transition:transform .22s ease;
}
.nav a:not(.btn):hover,.nav a.on{color:var(--ink)}
.nav a:not(.btn):hover:after,.nav a.on:after{transform:scaleX(1)}
.nav a.btn,.nav a.btn:hover{color:#fff}

/* ============ 按钮 ============ */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:8px;
  background:linear-gradient(135deg,var(--brand),var(--brand-2));
  color:#fff;border:1px solid transparent;padding:11px 20px;border-radius:12px;
  font-size:15px;font-weight:600;cursor:pointer;line-height:1.2;
  box-shadow:0 6px 16px -6px rgba(18,184,134,.6);
  transition:transform .16s cubic-bezier(.2,.8,.3,1), box-shadow .16s, filter .16s;
}
.btn:hover{transform:translateY(-2px);box-shadow:0 12px 26px -8px rgba(18,184,134,.7);filter:brightness(1.04)}
.btn:active{transform:translateY(0)}
.btn-lg{padding:14px 28px;font-size:16px;border-radius:14px}
.btn-sm{padding:7px 14px;font-size:14px;border-radius:10px}
.btn-block{width:100%;margin-top:12px}
.btn-ghost{background:var(--card);color:var(--ink);border-color:var(--line);box-shadow:var(--shadow-sm)}
.btn-ghost:hover{background:var(--card-2);box-shadow:var(--shadow)}
.linkbtn{background:none;border:0;color:var(--accent);cursor:pointer;font-size:14px;padding:0;font-weight:500}
.linkbtn:hover{text-decoration:underline}
.linkbtn.danger{color:var(--danger)}
.row-actions{display:flex;gap:12px;align-items:center;flex-wrap:wrap}
.row-actions form{display:inline}

/* ============ 卡片与栅格 ============ */
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow-sm)}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(268px,1fr));gap:22px}
.cols{display:grid;grid-template-columns:2fr 1fr;gap:20px;align-items:start}
.cols.wide{grid-template-columns:3fr 1fr}
.section{margin:56px 0}
.section-head{margin-bottom:22px;position:relative;padding-left:16px}
.section-head:before{
  content:'';position:absolute;left:0;top:6px;bottom:6px;width:4px;border-radius:4px;
  background:linear-gradient(180deg,var(--brand),var(--accent));
}
.page-title{margin:34px 0 20px}

/* 滚动入场：仅在 JS 可用时隐藏，避免脚本失效导致内容看不见 */
.js-reveal .reveal{opacity:0;transform:translateY(18px);
  transition:opacity .6s ease,transform .6s cubic-bezier(.2,.8,.3,1)}
.js-reveal .reveal.in{opacity:1;transform:none}

/* ============ 英雄区 ============ */
.hero{
  position:relative;overflow:hidden;isolation:isolate;
  display:grid;grid-template-columns:1.35fr .65fr;gap:28px;align-items:center;
  border-radius:var(--radius-lg);padding:clamp(32px,5vw,60px);margin-top:30px;
  color:#fff;background:linear-gradient(125deg,#0b7a5c 0%,#12b886 42%,#4c6ef5 100%);
  box-shadow:var(--shadow-lg);
}
.hero:before{
  content:'';position:absolute;inset:-40% -10% auto -10%;height:140%;z-index:-1;
  background:radial-gradient(40rem 20rem at 20% 10%, rgba(255,255,255,.28), transparent 60%),
             radial-gradient(30rem 16rem at 85% 80%, rgba(121,80,242,.45), transparent 65%);
  animation:drift 18s ease-in-out infinite alternate;
}
.hero:after{
  content:'';position:absolute;inset:0;z-index:-1;opacity:.16;
  background-image:linear-gradient(rgba(255,255,255,.7) 1px,transparent 1px),
                   linear-gradient(90deg,rgba(255,255,255,.7) 1px,transparent 1px);
  background-size:44px 44px;
  mask-image:radial-gradient(70% 60% at 50% 40%, #000 30%, transparent 100%);
  -webkit-mask-image:radial-gradient(70% 60% at 50% 40%, #000 30%, transparent 100%);
}
@keyframes drift{ from{transform:translate3d(-2%,-1%,0) scale(1)} to{transform:translate3d(3%,2%,0) scale(1.08)} }
.hero h1{font-size:clamp(30px,4.6vw,48px);text-shadow:0 2px 24px rgba(0,0,0,.18)}
.hero p{max-width:54ch;opacity:.94;font-size:clamp(15px,1.4vw,17px)}
.hero-actions{display:flex;gap:12px;margin:26px 0 22px;flex-wrap:wrap}
.hero .btn{background:#fff;color:var(--brand-ink);box-shadow:0 10px 26px -10px rgba(0,0,0,.5)}
.hero .btn:hover{box-shadow:0 16px 34px -12px rgba(0,0,0,.55)}
.hero .btn-ghost{background:rgba(255,255,255,.12);color:#fff;border-color:rgba(255,255,255,.5);backdrop-filter:blur(6px)}
.hero-stats{display:flex;gap:14px;flex-wrap:wrap}
.hero-stats > div{
  background:rgba(255,255,255,.14);border:1px solid rgba(255,255,255,.25);
  border-radius:14px;padding:12px 18px;min-width:104px;backdrop-filter:blur(8px);
}
.hero-stats strong{display:block;font-size:26px;font-weight:800;line-height:1.2}
.hero-stats span{opacity:.9;font-size:13px}

/* 漂浮公式 */
.hero-art{position:relative;height:210px}
.glyph{
  position:absolute;font-size:clamp(28px,3.4vw,46px);font-weight:700;opacity:.55;
  color:#fff;text-shadow:0 4px 18px rgba(0,0,0,.25);animation:float 7s ease-in-out infinite;
}
.glyph:nth-child(1){left:4%;top:8%}
.glyph:nth-child(2){left:44%;top:0%;animation-delay:-1.2s}
.glyph:nth-child(3){left:76%;top:22%;animation-delay:-2.4s}
.glyph:nth-child(4){left:12%;top:58%;animation-delay:-3.6s}
.glyph:nth-child(5){left:52%;top:64%;animation-delay:-4.8s}
.glyph:nth-child(6){left:84%;top:74%;animation-delay:-6s}
@keyframes float{ 0%,100%{transform:translateY(0) rotate(-3deg)} 50%{transform:translateY(-16px) rotate(4deg)} }

/* ============ 课程卡片 ============ */
.course-card{
  display:block;overflow:hidden;position:relative;background:var(--card);
  border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow-sm);
  transition:transform .22s cubic-bezier(.2,.8,.3,1), box-shadow .22s, border-color .22s;
}
.course-card:hover{transform:translateY(-6px);box-shadow:var(--glow);border-color:transparent}
.thumb{
  position:relative;height:132px;display:flex;align-items:center;justify-content:center;
  font-size:44px;color:#fff;overflow:hidden;
  background:linear-gradient(135deg,var(--brand),var(--accent));
}
.thumb:after{
  content:'';position:absolute;inset:0;opacity:.22;
  background-image:radial-gradient(circle at 20% 30%, #fff 1.5px, transparent 1.6px),
                   radial-gradient(circle at 70% 60%, #fff 1.5px, transparent 1.6px);
  background-size:26px 26px;
}
.course-card:nth-child(3n+2) .thumb{background:linear-gradient(135deg,#4c6ef5,#7950f2)}
.course-card:nth-child(3n) .thumb{background:linear-gradient(135deg,#f59f00,#e8590c)}
.thumb span{position:relative;z-index:1;transition:transform .3s}
.course-card:hover .thumb span{transform:scale(1.14) rotate(-6deg)}
.card-body{padding:18px}
.card-body h3{margin:8px 0;font-size:18px}
.tag{
  display:inline-block;font-size:12px;font-weight:600;color:var(--brand-ink);
  background:color-mix(in srgb, var(--brand) 14%, transparent);
  padding:3px 10px;border-radius:99px;
}
:root[data-theme="dark"] .tag{color:#5ee9b5}
.tag.premium{background:color-mix(in srgb, var(--gold) 18%, transparent);color:#b45309;margin-left:6px}
:root[data-theme="dark"] .tag.premium{color:#fcd34d}
.clamp{display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden;font-size:14px}
.meta{font-size:13px;color:var(--muted);margin-top:10px}

/* ============ 表单 ============ */
.filters{display:flex;gap:10px;margin-bottom:22px;flex-wrap:wrap}
input,select,textarea{
  font:inherit;padding:10px 13px;border:1px solid var(--line);border-radius:var(--radius-sm);
  background:var(--card);color:var(--ink);width:100%;transition:border-color .16s, box-shadow .16s;
}
input:focus,select:focus,textarea:focus{
  outline:none;border-color:var(--brand);
  box-shadow:0 0 0 3px color-mix(in srgb, var(--brand) 22%, transparent);
}
input[type=checkbox]{width:auto;accent-color:var(--brand)}
input[type=radio]{accent-color:var(--brand)}
label{display:block;margin-bottom:14px;font-size:14px;color:var(--muted)}
label input,label select,label textarea{margin-top:6px;color:var(--ink)}
label.check{display:flex;align-items:center;gap:8px}
.filters input,.filters select{width:auto;min-width:200px}
.inline-form{display:flex;gap:14px;flex-wrap:wrap;align-items:flex-end}
.inline-form label{flex:1;min-width:150px}
.auth{max-width:420px;margin:60px auto;padding:32px}

/* ============ 课程页 ============ */
.course-head{display:flex;justify-content:space-between;align-items:flex-start;gap:24px;margin:28px 0}
.progress-box{text-align:center}
.ring{
  width:84px;height:84px;border-radius:50%;display:flex;align-items:center;justify-content:center;
  font-weight:800;font-size:18px;margin:0 auto 8px;color:var(--brand-ink);
  background:conic-gradient(var(--brand) calc(var(--p,0) * 1%), var(--line) 0);
  position:relative;
}
:root[data-theme="dark"] .ring{color:#5ee9b5}
.ring:before{content:'';position:absolute;inset:7px;border-radius:50%;background:var(--bg)}
.ring span{position:relative;z-index:1}
.unit{margin-bottom:30px}
.unit-no{
  font-size:12px;font-weight:700;color:#fff;padding:3px 10px;border-radius:99px;vertical-align:middle;
  background:linear-gradient(135deg,var(--brand),var(--accent));
}
.lesson-list{list-style:none;padding:0;margin:0;background:var(--card);border:1px solid var(--line);
  border-radius:var(--radius);overflow:hidden;box-shadow:var(--shadow-sm)}
.lesson-list li+li{border-top:1px solid var(--line)}
.lesson-list a{display:flex;align-items:center;gap:14px;padding:15px 18px;transition:background .16s,padding .16s}
.lesson-list a:hover{background:var(--card-2);padding-left:24px}
.lesson-title{flex:1;font-weight:500}
.dot{
  width:30px;height:30px;border-radius:50%;border:2px solid var(--line);color:var(--muted);
  display:flex;align-items:center;justify-content:center;font-size:12px;flex:none;transition:.2s;
}
.lesson-list a:hover .dot{border-color:var(--brand);color:var(--brand)}
.dot.done{background:linear-gradient(135deg,var(--brand),var(--brand-2));border-color:transparent;color:#fff}
.dot.small{width:20px;height:20px;font-size:10px}

/* ============ 课时页 ============ */
.lesson-layout{display:grid;grid-template-columns:290px 1fr;gap:26px;margin-top:26px;align-items:start}
.sidebar{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:16px;
  position:sticky;top:86px;max-height:80vh;overflow:auto;box-shadow:var(--shadow-sm)}
.side-unit{font-size:12px;font-weight:700;color:var(--muted);margin:16px 0 6px;text-transform:uppercase;letter-spacing:.06em}
.side-lesson{display:flex;align-items:center;gap:9px;padding:8px 10px;border-radius:10px;font-size:14px;transition:.16s}
.side-lesson:hover{background:var(--card-2)}
.side-lesson.on{background:color-mix(in srgb, var(--brand) 14%, transparent);color:var(--brand-ink);font-weight:600}
:root[data-theme="dark"] .side-lesson.on{color:#5ee9b5}
.lesson-main{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:clamp(20px,3vw,32px);box-shadow:var(--shadow-sm)}
.player{position:relative;padding-top:56.25%;background:#000;border-radius:14px;overflow:hidden;
  margin-bottom:24px;box-shadow:var(--shadow)}
.player iframe,.player video{position:absolute;inset:0;width:100%;height:100%;border:0}
.prose{line-height:1.9;color:var(--ink-2);font-size:16.5px}
.prose img{max-width:100%;border-radius:12px}
.prose b{color:var(--ink)}
.lesson-actions{display:flex;align-items:center;gap:12px;margin-top:28px;flex-wrap:wrap}

/* ============ 练习 ============ */
.quiz{margin-top:36px;border-top:1px solid var(--line);padding-top:26px}
.question{margin-bottom:24px}
.q-prompt{font-weight:600;font-size:17px}
.option{
  display:flex;align-items:center;gap:10px;padding:12px 15px;border:1.5px solid var(--line);
  border-radius:12px;margin-bottom:9px;cursor:pointer;transition:.16s;background:var(--card);
}
.option:hover{border-color:var(--brand);background:var(--card-2);transform:translateX(3px)}
.option input{width:auto;margin:0}
.option:has(input:checked){border-color:var(--brand);background:color-mix(in srgb, var(--brand) 8%, transparent)}
.question.right .option:has(input:checked){border-color:var(--brand);background:color-mix(in srgb, var(--brand) 14%, transparent)}
.question.wrong .option:has(input:checked){border-color:var(--danger);background:color-mix(in srgb, var(--danger) 10%, transparent)}
.question.wrong{animation:shake .4s}
@keyframes shake{ 25%{transform:translateX(-6px)} 75%{transform:translateX(6px)} }
.feedback{font-size:14px;margin:6px 0 0}
.feedback.right{color:var(--brand-ink);font-weight:600}
:root[data-theme="dark"] .feedback.right{color:#5ee9b5}
.feedback.wrong{color:var(--danger);font-weight:600}
.score{font-weight:800;margin-top:14px;font-size:18px}

/* ============ 表格与后台 ============ */
.table{width:100%;border-collapse:collapse;font-size:14px}
.table th{text-align:left;color:var(--muted);font-weight:600;padding:10px 11px;
  border-bottom:1px solid var(--line);font-size:13px}
.table td{padding:12px 11px;border-bottom:1px solid var(--line);vertical-align:top}
.table tbody tr{transition:background .14s}
.table tbody tr:hover{background:var(--card-2)}
.table tr:last-child td{border-bottom:0}
.tablewrap{overflow-x:auto}
.tablewrap .table{min-width:860px}
.badge{font-size:12px;font-weight:600;padding:3px 10px;border-radius:99px;background:var(--bg-2);color:var(--muted);display:inline-block}
.badge.ok{background:color-mix(in srgb, var(--brand) 15%, transparent);color:var(--brand-ink)}
:root[data-theme="dark"] .badge.ok{color:#5ee9b5}
.badge.premium{background:color-mix(in srgb, var(--gold) 18%, transparent);color:#b45309}
.badge.tier1{background:color-mix(in srgb, var(--brand) 15%, transparent);color:var(--brand-ink)}
.badge.tier2{background:color-mix(in srgb, var(--accent) 15%, transparent);color:#3b5bdb}
.badge.tier3{background:color-mix(in srgb, var(--accent-2) 15%, transparent);color:#6741d9}
:root[data-theme="dark"] .badge.tier1{color:#5ee9b5}
:root[data-theme="dark"] .badge.tier2{color:#91a7ff}
:root[data-theme="dark"] .badge.tier3{color:#b197fc}
.tierline{font-size:13px;margin-bottom:4px}
.adminnav{display:flex;gap:6px;margin:20px 0;background:var(--card);border:1px solid var(--line);
  border-radius:14px;padding:6px;flex-wrap:wrap;box-shadow:var(--shadow-sm)}
.adminnav a{padding:9px 15px;border-radius:10px;font-size:14px;color:var(--muted);transition:.16s}
.adminnav a:hover{background:var(--card-2);color:var(--ink)}
.adminnav a.on{background:linear-gradient(135deg,var(--brand),var(--brand-2));color:#fff;
  box-shadow:0 6px 14px -6px rgba(18,184,134,.7)}
.stat-row{display:grid;grid-template-columns:repeat(auto-fit,minmax(148px,1fr));gap:16px;margin-bottom:22px}
.stat{padding:20px 16px;text-align:center;position:relative;overflow:hidden}
.stat:before{content:'';position:absolute;inset:0 0 auto 0;height:3px;
  background:linear-gradient(90deg,var(--brand),var(--accent))}
.stat strong{display:block;font-size:28px;font-weight:800;
  background:linear-gradient(120deg,var(--brand),var(--accent));
  -webkit-background-clip:text;background-clip:text;color:transparent}
.stat span{font-size:13px;color:var(--muted)}
.unit-admin{margin-bottom:18px}
.unit-admin-head{display:flex;justify-content:space-between;align-items:center;gap:12px}
.q-admin{border:1px solid var(--line);border-radius:12px;padding:14px;margin-bottom:14px;background:var(--card-2)}
.opts{margin:6px 0 8px}
.opts li.right{color:var(--brand-ink);font-weight:600}
:root[data-theme="dark"] .opts li.right{color:#5ee9b5}

/* ============ 提示 / 页脚 ============ */
.flash{margin-top:16px;padding:13px 16px;border-radius:12px;font-size:14px;font-weight:500;
  background:color-mix(in srgb, var(--brand) 12%, transparent);color:var(--brand-ink);
  border:1px solid color-mix(in srgb, var(--brand) 26%, transparent);
  animation:slidein .35s cubic-bezier(.2,.8,.3,1)}
:root[data-theme="dark"] .flash{color:#5ee9b5}
.flash.error{background:color-mix(in srgb, var(--danger) 10%, transparent);color:var(--danger);
  border-color:color-mix(in srgb, var(--danger) 26%, transparent)}
@keyframes slidein{ from{opacity:0;transform:translateY(-8px)} to{opacity:1;transform:none} }
.footer{margin-top:80px;padding:34px 0;border-top:1px solid var(--line);color:var(--muted);font-size:14px;
  background:var(--card)}

/* ============ 语言 / 主题切换 ============ */
.langswitch{display:inline-flex;border:1px solid var(--line);border-radius:99px;overflow:hidden;background:var(--card)}
.langswitch a{padding:5px 12px;font-size:13px;color:var(--muted)}
.langswitch a:after{display:none}
.langswitch a.on{background:linear-gradient(135deg,var(--brand),var(--brand-2));color:#fff}
.themebtn{background:var(--card);border:1px solid var(--line);border-radius:99px;width:36px;height:36px;
  cursor:pointer;font-size:15px;line-height:1;transition:.18s;color:var(--ink)}
.themebtn:hover{transform:rotate(-18deg) scale(1.08);border-color:var(--brand)}

/* ============ 付费 ============ */
.paywall-banner{display:flex;align-items:center;justify-content:space-between;gap:20px;padding:22px;
  margin-bottom:26px;border:1px solid color-mix(in srgb, var(--gold) 34%, transparent);
  background:linear-gradient(120deg, color-mix(in srgb, var(--gold) 10%, var(--card)), var(--card));
  border-radius:var(--radius)}
.paywall-banner p{margin:4px 0 0}
.paywall{text-align:center;padding:48px 26px;border:1px solid color-mix(in srgb, var(--gold) 34%, transparent);
  background:linear-gradient(160deg, color-mix(in srgb, var(--gold) 10%, var(--card)), var(--card))}
.paywall-icon{font-size:44px;animation:float 5s ease-in-out infinite}
.lesson-list a.locked .lesson-title{color:var(--muted)}
.price{font-size:18px}
.price strong{font-size:28px;background:linear-gradient(120deg,var(--brand),var(--accent));
  -webkit-background-clip:text;background-clip:text;color:transparent}

/* ============ 分销 ============ */
.link-box{display:flex;align-items:center;justify-content:space-between;gap:18px;margin-bottom:22px}
.linkcode{display:inline-block;background:var(--bg-2);border-radius:8px;padding:5px 10px;font-size:13px;
  word-break:break-all;margin-right:8px;font-family:ui-monospace,SFMono-Regular,Menlo,monospace}

/* ============ AI 助理 ============ */
.ai-fab{
  position:fixed;right:24px;bottom:24px;z-index:40;border:0;border-radius:99px;
  padding:13px 22px;font-size:15px;font-weight:600;cursor:pointer;color:#fff;
  background:linear-gradient(135deg,var(--accent),var(--accent-2));
  box-shadow:0 10px 30px -8px rgba(76,110,245,.7);
  transition:transform .2s cubic-bezier(.2,.8,.3,1), box-shadow .2s;
  animation:pulse 3.2s ease-in-out infinite;
}
.ai-fab:hover{transform:translateY(-3px) scale(1.03);box-shadow:0 16px 38px -10px rgba(76,110,245,.8)}
.ai-fab.hidden{display:none}
@keyframes pulse{ 0%,100%{box-shadow:0 10px 30px -8px rgba(76,110,245,.7)}
                  50%{box-shadow:0 10px 34px -6px rgba(121,80,242,.85)} }
.ai-panel{
  position:fixed;right:24px;bottom:24px;z-index:41;width:392px;max-width:calc(100vw - 32px);
  height:540px;max-height:calc(100vh - 48px);background:var(--card);border:1px solid var(--line);
  border-radius:20px;box-shadow:var(--shadow-lg);display:flex;flex-direction:column;overflow:hidden;
  animation:panelin .28s cubic-bezier(.2,.8,.3,1);
}
.ai-panel[hidden]{display:none}
@keyframes panelin{ from{opacity:0;transform:translateY(16px) scale(.97)} to{opacity:1;transform:none} }
.ai-head{display:flex;align-items:center;justify-content:space-between;padding:15px 18px;
  border-bottom:1px solid var(--line);
  background:linear-gradient(120deg, color-mix(in srgb, var(--accent) 12%, var(--card)), var(--card))}
.ai-log{flex:1;overflow:auto;padding:16px;display:flex;flex-direction:column;gap:11px}
.ai-msg{padding:10px 14px;border-radius:15px;font-size:14px;line-height:1.65;max-width:88%;
  white-space:pre-wrap;animation:slidein .25s ease}
.ai-msg.bot{background:var(--bg-2);align-self:flex-start;border-bottom-left-radius:5px}
.ai-msg.me{background:linear-gradient(135deg,var(--accent),var(--accent-2));color:#fff;
  align-self:flex-end;border-bottom-right-radius:5px}
.ai-msg.pending{opacity:.65}
.ai-msg a{color:var(--accent);text-decoration:underline}
.ai-msg.me a{color:#fff}
.ai-form{display:flex;gap:9px;padding:13px;border-top:1px solid var(--line);align-items:flex-end}
.ai-form textarea{resize:none}

/* ============ 响应式与动效偏好 ============ */
@media (max-width:900px){
  .cols,.cols.wide,.hero,.lesson-layout{grid-template-columns:1fr}
  .hero-art{display:none}
  .sidebar{position:static;max-height:none}
  .paywall-banner{flex-direction:column;align-items:flex-start}
}
@media (max-width:520px){ .ai-panel{height:72vh;right:12px;bottom:12px} .ai-fab{right:14px;bottom:14px} }
@media (prefers-reduced-motion:reduce){
  *,*:before,*:after{animation-duration:.001ms !important;animation-iteration-count:1 !important;
    transition-duration:.001ms !important;scroll-behavior:auto !important}
  .js-reveal .reveal{opacity:1;transform:none}
}

/* 首页补充 */
.hero-badge{display:inline-block;font-size:13px;font-weight:600;letter-spacing:.04em;
  background:rgba(255,255,255,.18);border:1px solid rgba(255,255,255,.32);
  padding:5px 14px;border-radius:99px;margin-bottom:18px;backdrop-filter:blur(6px)}
.feat-grid{grid-template-columns:repeat(auto-fit,minmax(230px,1fr))}
.feat{padding:24px;transition:transform .22s cubic-bezier(.2,.8,.3,1),box-shadow .22s}
.feat:hover{transform:translateY(-4px);box-shadow:var(--shadow)}
.feat h3{font-size:17px;margin:12px 0 6px}
.feat p{font-size:14px;margin:0}
.feat-icon{width:46px;height:46px;border-radius:13px;display:flex;align-items:center;justify-content:center;
  font-size:22px;background:linear-gradient(135deg,color-mix(in srgb,var(--brand) 18%,transparent),
  color-mix(in srgb,var(--accent) 18%,transparent))}
.arrow{display:inline-block;transition:transform .22s;color:var(--brand)}
.course-card:hover .arrow{transform:translateX(5px)}
.ai-form .btn{white-space:nowrap;flex:none;align-self:stretch}

/* 小屏适配 */
@media (max-width:640px){
  .wrap{padding:0 16px}
  .topbar-inner{height:auto;padding:10px 16px;flex-wrap:wrap;gap:10px}
  .brand{font-size:18px;white-space:nowrap}
  .nav{width:100%;gap:14px;font-size:14px;justify-content:flex-start;align-items:center}
  .nav a{font-size:14px}
  .themebtn{width:32px;height:32px;font-size:14px;margin-left:auto}
  .hero{padding:26px 20px;margin-top:18px;border-radius:20px}
  .hero-actions{margin:20px 0 18px}
  .hero-actions .btn{flex:1;justify-content:center}
  .hero-stats{display:grid;grid-template-columns:repeat(3,1fr);gap:10px}
  .hero-stats > div{min-width:0;padding:10px 8px;text-align:center}
  .hero-stats strong{font-size:20px}
  .hero-stats span{font-size:11px}
  .section{margin:40px 0}
  .course-head{flex-direction:column}
  .lesson-list a{padding:13px 14px;gap:10px}
  .stat-row{grid-template-columns:repeat(2,1fr)}
  .auth{margin:28px auto;padding:24px}
  .link-box{flex-direction:column;align-items:flex-start}
}

/* 讲师 */
.teacher-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(320px,1fr));gap:20px}
.teacher{display:flex;gap:18px;padding:20px;align-items:flex-start;
  transition:transform .22s cubic-bezier(.2,.8,.3,1),box-shadow .22s}
.teacher:hover{transform:translateY(-3px);box-shadow:var(--shadow)}
.teacher-photo{width:96px;height:96px;border-radius:20px;object-fit:cover;object-position:center top;
  flex:none;box-shadow:var(--shadow-sm);border:2px solid var(--line)}
.teacher-ph{display:flex;align-items:center;justify-content:center;font-size:34px;font-weight:800;color:#fff;
  background:linear-gradient(135deg,var(--brand),var(--accent));border-color:transparent}
.teacher-info h3{margin:0 0 4px;font-size:18px}
.teacher-title{font-size:13px;font-weight:600;color:var(--brand-ink);margin-bottom:8px}
:root[data-theme="dark"] .teacher-title{color:#5ee9b5}
.teacher-info p{font-size:14px;margin:0}
.coming{padding:48px 24px}
.coming-icon{font-size:40px;margin-bottom:8px}
.avatar{width:52px;height:52px;border-radius:12px;object-fit:cover;object-position:center top;display:block}
.avatar-ph{display:flex;align-items:center;justify-content:center;font-weight:700;color:#fff;
  background:linear-gradient(135deg,var(--brand),var(--accent))}
.bio-cell{max-width:280px}
.pick-list{border:1px solid var(--line);border-radius:10px;padding:12px;margin-bottom:14px;background:var(--card-2)}
.pick-list label{margin-bottom:6px}

/* 课件下载 */
.attach{display:flex;align-items:center;gap:14px;margin-top:22px;padding:16px 18px;
  border:1px solid var(--line);border-radius:14px;background:var(--card-2);
  transition:transform .18s,box-shadow .18s,border-color .18s}
.attach:hover{transform:translateY(-2px);box-shadow:var(--shadow);border-color:var(--brand)}
.attach-icon{font-size:26px}
.attach .muted{font-size:13px}
.tag.draft{background:var(--bg-2);color:var(--muted);margin-left:6px}
video::cue{font-size:.85em;background:rgba(0,0,0,.72)}

/* 首页讲师大卡 */
.home-teachers{grid-template-columns:repeat(auto-fit,minmax(400px,1fr))}
.teacher-lg{padding:24px;gap:22px}
.teacher-lg .teacher-photo{width:132px;height:158px;border-radius:18px}
.teacher-lg .teacher-info h3{font-size:20px}
.teacher-lg .teacher-info p{font-size:14.5px;line-height:1.75}
@media (max-width:640px){
  .home-teachers{grid-template-columns:1fr}
  .teacher-lg{flex-direction:column;align-items:center;text-align:center}
  .teacher-lg .teacher-photo{width:120px;height:144px}
}

/* AI 助理：图片上传 */
.ai-upload{display:flex;align-items:center;justify-content:center;width:40px;height:40px;flex:none;
  border:1px solid var(--line);border-radius:10px;cursor:pointer;font-size:18px;background:var(--card);
  transition:.16s}
.ai-upload:hover{border-color:var(--accent);background:var(--card-2);transform:translateY(-1px)}
.ai-preview{display:flex;align-items:center;gap:10px;padding:10px 13px;border-top:1px solid var(--line);
  background:var(--card-2)}
.ai-preview[hidden]{display:none}
.ai-preview img{width:56px;height:56px;object-fit:cover;border-radius:8px;border:1px solid var(--line)}
.ai-msg-img{display:block;max-width:100%;border-radius:10px;margin-bottom:6px}