:root{--bg:#f4f7fb;--ink:#17233b;--muted:#70809b;--line:#dfe7f1;--blue:#2878f0;--cyan:#16b6cf;--teal:#139e91;--orange:#f6a623;--red:#e75361;--card:#fff;--shadow:0 18px 45px rgba(35,64,108,.10)}
*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font-family:Inter,"PingFang SC","Microsoft YaHei",sans-serif}a{text-decoration:none;color:inherit}.app-shell{min-height:100vh}.topbar{height:70px;background:#fff;border-bottom:1px solid var(--line);display:flex;align-items:center;padding:0 max(24px,calc((100vw - 1180px)/2));gap:42px;position:sticky;top:0;z-index:10}.brand{font-weight:800;font-size:19px;display:flex;align-items:center;gap:10px}.brand-mark{width:35px;height:35px;border-radius:10px;background:linear-gradient(135deg,var(--blue),var(--cyan));color:#fff;display:grid;place-items:center;font-size:12px;letter-spacing:.3px}.topbar nav{display:flex;gap:26px;color:#65738c;font-size:14px}.topbar nav a:hover{color:var(--blue)}.sync-dot{margin-left:auto;font-size:12px;color:var(--teal);display:flex;gap:7px;align-items:center}.sync-dot i{width:7px;height:7px;background:#27c59a;border-radius:50%;box-shadow:0 0 0 4px #e0fbf1}.page{max-width:1180px;margin:0 auto;padding:58px 24px 80px}.hero{display:grid;grid-template-columns:1.1fr .9fr;gap:70px;align-items:center}.eyebrow{font-size:12px;letter-spacing:2px;color:var(--blue);font-weight:700;text-transform:uppercase}.hero h1{font-size:clamp(38px,5vw,66px);line-height:1.1;margin:15px 0 18px;letter-spacing:0}.hero p{font-size:17px;line-height:1.8;color:var(--muted);max-width:590px}.hero-visual{min-height:340px;display:grid;place-items:center;position:relative}.orbit{width:290px;height:290px;border:1px solid #cfdceb;border-radius:50%;position:relative;transform:rotate(-12deg)}.orbit:before,.orbit:after{content:"";position:absolute;border:1px dashed #b9cce5;border-radius:50%}.orbit:before{inset:35px;transform:rotate(45deg)}.orbit:after{inset:72px;transform:rotate(-25deg)}.orbit-core{position:absolute;inset:80px;border-radius:50%;background:linear-gradient(145deg,#edf6ff,#fff);box-shadow:var(--shadow);display:grid;place-items:center;transform:rotate(12deg)}.orbit-core 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p{color:var(--muted);font-size:13px;line-height:1.6;min-height:42px}.exam-meta{display:flex;gap:10px;color:#8a98ad;font-size:12px;margin-top:auto}.btn{border:0;border-radius:8px;padding:12px 17px;font-weight:700;cursor:pointer;font-size:14px;display:inline-flex;align-items:center;justify-content:center;gap:8px}.btn-primary{background:linear-gradient(135deg,var(--blue),var(--cyan));color:#fff}.btn-light{background:#eef4fb;color:#38618d}.btn-danger{background:#fff0f2;color:#c94355}.btn:disabled{opacity:.45;cursor:not-allowed}.exam-card .btn{margin-top:16px}.modal-layer{position:fixed;inset:0;background:rgba(22,35,59,.58);display:grid;place-items:center;padding:20px;z-index:30}.modal{background:#fff;border-radius:14px;padding:28px;max-width:450px;width:100%;box-shadow:0 24px 70px rgba(0,0,0,.2)}.modal h2{margin:0 0 8px}.modal p{color:var(--muted);font-size:14px}.field{display:grid;gap:7px;margin:15px 0}.field label{font-size:13px;font-weight:700}.field input,.field textarea,.field 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input[type=file]{width:100%;margin:10px 0 13px}.empty{color:var(--muted);font-size:13px;padding:15px 0}.toast{position:fixed;bottom:22px;right:22px;background:#17233b;color:#fff;padding:12px 16px;border-radius:8px;z-index:50;box-shadow:var(--shadow)}footer{text-align:center;color:#97a4b7;font-size:12px;padding:22px}@media(max-width:800px){.hero{grid-template-columns:1fr;gap:20px}.hero-visual{min-height:250px}.exam-grid,.dashboard-grid{grid-template-columns:1fr}.two-col{grid-template-columns:1fr}.topbar{padding:0 16px;gap:15px}.topbar nav{gap:13px}.topbar nav a{font-size:12px}.page{padding:35px 16px}.question-card{padding:20px}.question-card h2{font-size:21px}.teacher-head{display:block}.teacher-head .btn{margin-top:14px}}