:root{--primary:#1677ff;--primary-dark:#0d63dc;--ink:#172235;--muted:#718096;--line:#e7edf5;--bg:#f6f8fc;--panel:#fff;--success:#18a66a;--danger:#d94848;--shadow:0 8px 28px rgba(31,55,87,.07);--radius:14px}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--ink);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",Arial,sans-serif;line-height:1.6;padding-bottom:0}a{text-decoration:none;color:inherit}button,input,select,textarea{font:inherit}.topbar{height:68px;background:rgba(255,255,255,.96);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:50;backdrop-filter:blur(14px)}.top-inner{max-width:1440px;height:100%;margin:auto;padding:0 24px;display:flex;align-items:center;gap:28px}.brand{display:flex;align-items:center;gap:9px;font-weight:900;white-space:nowrap}.brand-mark{width:34px;height:34px;border-radius:10px;display:grid;place-items:center;background:linear-gradient(135deg,#1677ff,#55a8ff);color:#fff;font-size:11px;box-shadow:0 7px 16px rgba(22,119,255,.25)}.brand-text{font-size:20px;color:#172235}.brand-text span{color:var(--primary)}.main-nav{display:flex;align-items:center;gap:4px;height:100%}.main-nav a{height:42px;padding:0 14px;display:flex;align-items:center;border-radius:9px;font-size:14px;font-weight:650;color:#566579}.main-nav a:hover,.main-nav a.active{background:#edf5ff;color:var(--primary)}.top-right{margin-left:auto;display:flex;align-items:center;gap:10px}.search{height:40px;width:235px;border:1px solid #dfe7f1;border-radius:22px;display:flex;align-items:center;padding:0 13px;color:#9aa7b8;background:#f9fbfe}.search:focus-within{border-color:#8dbfff;background:#fff;box-shadow:0 0 0 3px #1677ff12}.search input{border:0;outline:0;background:transparent;width:100%;padding-left:7px;color:var(--ink)}.login-link{padding:9px 11px;color:#506078;font-weight:650}.register{background:var(--primary);color:#fff!important;border-radius:9px;padding:10px 16px;font-weight:700}.register:hover{background:var(--primary-dark)}.account-menu{position:relative}.account-trigger{border:1px solid #e0e7f0;background:#fff;border-radius:22px;height:40px;padding:0 10px 0 6px;display:flex;align-items:center;gap:7px;color:#4f5e72;cursor:pointer}.account-trigger b{font-size:12px;color:#8995a6}.avatar{width:28px;height:28px;border-radius:50%;display:grid;place-items:center;background:#edf5ff;font-size:14px}.account-popover{display:none;position:absolute;right:0;top:48px;width:180px;background:#fff;border:1px solid var(--line);border-radius:12px;padding:7px;box-shadow:0 16px 35px rgba(20,39,68,.15)}.account-menu.open .account-popover{display:block}.account-popover a{display:block;padding:9px 10px;border-radius:8px;font-size:13px;color:#526177}.account-popover a:hover{background:#f2f7ff;color:var(--primary)}.popover-line{height:1px;background:var(--line);margin:5px 2px}.account-popover .logout-link{color:#d94848}.menu{display:none;border:0;background:#f2f6fb;color:#334155;border-radius:9px;width:40px;height:40px;font-size:20px;cursor:pointer}.hero{max-width:1440px;margin:18px auto 0;min-height:340px;border-radius:18px;background:linear-gradient(110deg,#0e73f5,#65bdf7);color:#fff;position:relative;overflow:hidden;box-shadow:0 14px 35px rgba(35,109,194,.16)}.hero:after{content:"";position:absolute;inset:0;background:radial-gradient(circle at 75% 30%,rgba(255,255,255,.18),transparent 30%);pointer-events:none}.hero-copy{position:relative;margin-left:8%;padding-top:62px;z-index:2;max-width:650px}.pill{display:inline-flex;background:#ffffff1f;border:1px solid #ffffff35;border-radius:999px;padding:7px 14px;font-size:13px;font-weight:700}.hero h1{font-size:clamp(38px,5vw,56px);line-height:1.18;margin:17px 0 10px;letter-spacing:-1px}.hero p{font-size:17px;margin:0 0 25px;opacity:.92}.btn-white{display:inline-flex;align-items:center;background:#fff;color:var(--primary);padding:12px 23px;border-radius:10px;font-weight:800;box-shadow:0 8px 18px rgba(5,61,131,.14)}.hero-art{position:absolute;right:6%;bottom:-20px;width:470px;height:280px;opacity:.9}.book{position:absolute;width:270px;height:50px;border-radius:7px;right:100px;bottom:42px;background:#fff;transform:rotate(-5deg);box-shadow:0 12px 22px #084a9b44}.book.two{bottom:89px;background:#d8b8fa}.book.three{bottom:136px;background:#eef5ff}.hat{position:absolute;right:120px;top:5px;font-size:90px;color:#1551bb}.bubble{position:absolute;right:-10px;top:68px;width:195px;background:#3a9cf466;border:1px solid #ffffff55;border-radius:14px;padding:15px}.bubble b{display:block;font-size:17px}.wrap{max-width:1440px;margin:auto;padding:0 24px 54px}.section-head{display:flex;justify-content:space-between;align-items:end;margin:34px 0 17px}.section-head h2{margin:0;font-size:25px;letter-spacing:-.3px}.section-head p{margin:5px 0 0;color:#7d899a;font-size:14px}.section-head>a{color:var(--primary);font-size:14px;font-weight:650}.subjects{display:grid;grid-template-columns:repeat(4,1fr);gap:16px}.subject{min-height:118px;border-radius:14px;padding:19px;display:flex;align-items:center;gap:15px;border:1px solid}.subject i{width:54px;height:54px;border-radius:15px;display:grid;place-items:center;color:#fff;font-style:normal;font-size:26px;font-weight:900;flex:none}.subject b{display:block;font-size:18px}.subject small{color:#758398;font-size:12px}.subject strong{margin-left:auto;font-size:21px;color:#6c7b8f}.math{background:#edf5ff;border-color:#dceaff}.math i{background:#3b98f6}.physics{background:#ecfff6;border-color:#d6f3e5}.physics i{background:#31b982}.chemistry{background:#fff4ea;border-color:#ffe0ca}.chemistry i{background:#ff8d3c}.english{background:#f4efff;border-color:#e6dbff}.english i{background:#8a50e8}.course-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:18px}.course-card{background:#fff;border:1px solid #e4eaf2;border-radius:14px;overflow:hidden;box-shadow:var(--shadow);transition:transform .18s,box-shadow .18s}.course-card:hover{transform:translateY(-3px);box-shadow:0 14px 30px rgba(31,55,87,.11)}.cover{height:155px;padding:15px;color:#fff;position:relative}.cover .tag{background:#0002;border-radius:14px;padding:5px 9px;font-size:12px}.cover .subject-mark{position:absolute;right:18px;bottom:2px;font-size:62px;opacity:.3;font-weight:900}.cover.math{background:linear-gradient(135deg,#2f91fa,#6ebcfb)}.cover.physics{background:linear-gradient(135deg,#25b77d,#61d7a4)}.cover.chemistry{background:linear-gradient(135deg,#ff8b39,#ffb26f)}.cover.english{background:linear-gradient(135deg,#8050e7,#ae85ff)}.card-body{padding:15px}.card-body h3{font-size:17px;margin:0 0 6px}.card-body p{height:44px;overflow:hidden;color:#778598;font-size:13px;margin:0 0 11px}.meta{font-size:12px;color:#8b97a7;display:flex;justify-content:space-between}.page{max-width:1180px;margin:30px auto;padding:0 20px 50px}.panel{background:#fff;border:1px solid #e4eaf2;border-radius:14px;padding:24px;box-shadow:var(--shadow)}.filters{display:flex;gap:9px;flex-wrap:wrap;margin:20px 0}.filters a,.filter-btn{padding:8px 14px;border:1px solid #dce4ee;border-radius:20px;background:#fff;color:#607087}.filters a.active,.filter-btn.active{background:#eaf3ff;color:var(--primary);border-color:#bcd9ff}.form-box{max-width:470px;margin:55px auto}.form-box h1{text-align:center}.form-row{margin:15px 0}.form-row label{display:block;font-weight:650;margin-bottom:7px}.form-row input,.form-row textarea,.form-row select{width:100%;border:1px solid #dbe3ed;border-radius:9px;padding:12px;outline:0;background:#fff}.form-row input:focus,.form-row textarea:focus,.form-row select:focus{border-color:#65a9ff;box-shadow:0 0 0 3px #1677ff10}.full-btn{width:100%;border:0;cursor:pointer;padding:12px}.error{background:#fff0f0;color:#c63b3b;border:1px solid #ffd4d4;padding:10px;border-radius:8px}.success{background:#edfff5;color:#198653;border:1px solid #ccefe0;padding:10px;border-radius:8px}.detail{display:grid;grid-template-columns:1.5fr 1fr;gap:22px}.lesson-list{list-style:none;padding:0;margin:0}.lesson-list li{border-bottom:1px solid #edf1f5}.lesson-list a{display:flex;justify-content:space-between;padding:13px 4px}.video{background:#0e1622;border-radius:12px;overflow:hidden;aspect-ratio:16/9;display:grid;place-items:center;color:#fff}.video video{width:100%;height:100%}.video-placeholder{text-align:center}.progress{height:8px;background:#e8eef6;border-radius:5px;overflow:hidden}.progress i{display:block;height:100%;background:var(--primary)}.quiz{margin-top:15px}.question{padding:18px 0;border-bottom:1px solid #edf1f5}.question label{display:block;padding:7px 0}.ai-layout{display:grid;grid-template-columns:250px 1fr;gap:20px}.ai-menu a{display:block;padding:12px;border-radius:9px}.ai-menu a:hover{background:#eef5ff;color:var(--primary)}.chat{min-height:540px;display:flex;flex-direction:column}.messages{flex:1;overflow:auto;padding:10px}.msg{max-width:78%;padding:12px 15px;border-radius:12px;margin:10px 0;white-space:pre-wrap}.msg.ai{background:#f0f5fb}.msg.me{margin-left:auto;background:var(--primary);color:#fff}.chat-form{display:flex;gap:10px;border-top:1px solid #edf1f5;padding-top:15px}.chat-form textarea{flex:1;resize:none}.dash-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:15px}.stat{background:#fff;border:1px solid #e3eaf2;border-radius:12px;padding:20px}.stat strong{font-size:30px;display:block;color:var(--primary)}.table{width:100%;border-collapse:collapse}.table th,.table td{padding:11px;border-bottom:1px solid #edf1f5;text-align:left}.admin-nav{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:20px}.admin-nav a{padding:8px 13px;background:#fff;border:1px solid #e1e8f0;border-radius:7px}.admin-actions{display:flex;gap:8px;flex-wrap:wrap}.btn-danger{background:#fff0f0;color:#c33;border:1px solid #ffd0d0;padding:7px 11px;border-radius:7px}.btn-secondary{background:#fff;border:1px solid #d9e2ed;padding:9px 14px;border-radius:7px}.empty{padding:40px;text-align:center;color:#8996a8}footer{background:#111a25;color:#a3afbf;padding:30px 24px}.footer-inner{max-width:1440px;margin:auto;display:flex;justify-content:space-between;gap:20px}.footer-inner b{color:#fff;font-size:18px}.footer-inner p{margin:4px 0}.mobile-bottom-nav{display:none}
@media(max-width:1150px){.top-inner{gap:14px}.main-nav a{padding:0 10px}.search{width:190px}.course-grid{grid-template-columns:repeat(3,1fr)}.hero-art{right:-80px;opacity:.5}.subjects{grid-template-columns:repeat(2,1fr)}}
@media(max-width:800px){body{padding-bottom:64px}.topbar{height:60px}.top-inner{padding:0 14px}.brand-mark{width:31px;height:31px}.brand-text{font-size:18px}.top-right{display:none}.menu{display:block;margin-left:auto}.main-nav{display:none;position:fixed;top:60px;left:10px;right:10px;height:auto;background:#fff;border:1px solid var(--line);border-radius:14px;box-shadow:0 15px 35px rgba(20,39,68,.15);padding:8px;flex-direction:column;align-items:stretch;gap:2px}.main-nav.open{display:flex}.main-nav a{height:44px;padding:0 13px}.hero{margin:0;border-radius:0 0 16px 16px;min-height:360px}.hero-copy{margin-left:0;padding:52px 22px}.hero h1{font-size:39px}.hero p{font-size:15px}.hero-art{display:none}.wrap{padding-left:16px;padding-right:16px}.section-head{margin-top:27px}.course-grid{grid-template-columns:repeat(2,1fr)}.subjects{grid-template-columns:repeat(2,1fr)}.detail,.ai-layout{grid-template-columns:1fr}.dash-grid{grid-template-columns:repeat(2,1fr)}.page{margin-top:18px;padding-left:14px;padding-right:14px}.panel{padding:18px}.mobile-bottom-nav{position:fixed;left:0;right:0;bottom:0;height:64px;background:rgba(255,255,255,.97);border-top:1px solid var(--line);display:grid;grid-template-columns:repeat(5,1fr);z-index:60;backdrop-filter:blur(14px)}.mobile-bottom-nav a{display:flex;flex-direction:column;align-items:center;justify-content:center;color:#7a8799;gap:1px;font-size:18px}.mobile-bottom-nav a:hover,.mobile-bottom-nav a.active{color:var(--primary)}.mobile-bottom-nav small{font-size:10px}}
@media(max-width:520px){.subjects,.course-grid,.dash-grid{grid-template-columns:1fr}.section-head{display:block}.section-head>a{display:inline-block;margin-top:8px}.course-card .cover{height:145px}.form-box{margin:28px auto}.footer-inner{display:block}.footer-inner>div+div{margin-top:14px}.table-wrap{overflow-x:auto}.table{min-width:650px}.chat{min-height:470px}.msg{max-width:90%}}