:root{--brand: #4f46e5;--brand-dark: #4338ca;--brand-light: #eef2ff;--accent: #0ea5e9;--success: #16a34a;--success-bg: #ecfdf5;--danger: #dc2626;--danger-bg: #fef2f2;--warning: #d97706;--ink: #111827;--ink-2: #374151;--muted: #6b7280;--line: #e5e7eb;--bg: #f5f6fa;--card: #ffffff;--radius: 16px;--shadow: 0 1px 2px rgba(16, 24, 40, .04), 0 12px 32px rgba(16, 24, 40, .06)}*{box-sizing:border-box}html,body,#root{min-height:100%}body{margin:0;background:var(--bg);color:var(--ink);font-family:-apple-system,BlinkMacSystemFont,Segoe UI,PingFang SC,Hiragino Sans GB,Microsoft YaHei,Helvetica Neue,Arial,sans-serif;font-size:15px;line-height:1.65;-webkit-font-smoothing:antialiased}a{color:var(--brand);text-decoration:none}a:hover{color:var(--brand-dark)}button{font-family:inherit;cursor:pointer}input,textarea{font-family:inherit;font-size:15px}.app-shell{display:flex;flex-direction:column;min-height:100vh}.navbar{position:sticky;top:0;z-index:20;display:flex;align-items:center;gap:24px;padding:0 28px;height:64px;background:linear-gradient(100deg,#312e81,#4f46e5 55%,#6366f1);color:#fff;box-shadow:0 2px 12px #312e8140}.navbar .logo{display:flex;align-items:center;gap:10px;color:#fff;font-weight:700;font-size:17px;letter-spacing:.5px}.logo-badge{display:grid;place-items:center;width:32px;height:32px;border-radius:10px;background:#ffffff2e;font-size:17px}.navbar nav{display:flex;gap:4px;flex:1}.navbar nav a{padding:8px 14px;border-radius:10px;color:#ffffffd1;font-size:14px;font-weight:500;transition:background .15s,color .15s}.navbar nav a:hover{background:#ffffff24;color:#fff}.navbar nav a.active{background:#ffffff38;color:#fff}.nav-user{display:flex;align-items:center;gap:12px;font-size:14px}.nav-user .avatar{display:grid;place-items:center;width:32px;height:32px;border-radius:50%;background:#fff3;font-weight:600}.main{flex:1;width:100%;max-width:1160px;margin:0 auto;padding:28px 24px 64px}.footer{padding:20px 24px;text-align:center;color:var(--muted);font-size:13px;border-top:1px solid var(--line);background:#fff}.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow)}.section-title{display:flex;align-items:baseline;justify-content:space-between;gap:16px;margin:32px 0 16px}.section-title h2{margin:0;font-size:20px;letter-spacing:.2px}.section-title p{margin:0;color:var(--muted);font-size:13px}.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:10px 18px;border:1px solid transparent;border-radius:10px;background:var(--brand);color:#fff;font-size:14px;font-weight:600;transition:background .15s,transform .1s,opacity .15s}.btn:hover:not(:disabled){background:var(--brand-dark)}.btn:active:not(:disabled){transform:translateY(1px)}.btn:disabled{opacity:.55;cursor:not-allowed}.btn.ghost{background:#fff;border-color:var(--line);color:var(--ink-2)}.btn.ghost:hover:not(:disabled){background:var(--brand-light);border-color:#c7d2fe;color:var(--brand-dark)}.btn.danger{background:var(--danger)}.btn.small{padding:6px 12px;font-size:13px;border-radius:8px}.btn.block{width:100%}.tag{display:inline-flex;align-items:center;padding:2px 10px;border-radius:999px;background:var(--brand-light);color:var(--brand-dark);font-size:12px;font-weight:600}.tag.green{background:var(--success-bg);color:var(--success)}.tag.gray{background:#f3f4f6;color:var(--muted)}.tag.amber{background:#fffbeb;color:var(--warning)}.alert{padding:12px 16px;border-radius:12px;font-size:14px;border:1px solid}.alert.error{background:var(--danger-bg);border-color:#fecaca;color:#991b1b}.alert.info{background:var(--brand-light);border-color:#c7d2fe;color:var(--brand-dark)}.empty{padding:48px 24px;text-align:center;color:var(--muted)}.skeleton{height:14px;border-radius:8px;background:linear-gradient(90deg,#eef0f4 25%,#e3e6ec 37%,#eef0f4 63%);background-size:400% 100%;animation:shimmer 1.3s ease infinite}@keyframes shimmer{0%{background-position:100% 50%}to{background-position:0 50%}}.hero{position:relative;overflow:hidden;padding:40px 36px;border-radius:22px;color:#fff;background:linear-gradient(120deg,#312e81,#4f46e5 45%,#7c3aed);box-shadow:0 18px 40px #4f46e547}.hero h1{margin:0 0 10px;font-size:32px;line-height:1.3}.hero p{margin:0 0 24px;max-width:640px;color:#ffffffdb}.hero-actions{display:flex;flex-wrap:wrap;gap:12px}.hero .btn{background:#fff;color:var(--brand-dark)}.hero .btn.ghost{background:#ffffff1f;border-color:#ffffff73;color:#fff}.stat-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(180px,1fr));gap:16px;margin-top:20px}.stat{padding:18px 20px;border-radius:14px;background:#fff;border:1px solid var(--line)}.stat .label{color:var(--muted);font-size:13px}.stat .value{margin-top:6px;font-size:26px;font-weight:700;color:var(--brand-dark)}.lesson-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:16px}.lesson-card{display:flex;flex-direction:column;gap:10px;padding:20px;border-radius:var(--radius);background:#fff;border:1px solid var(--line);transition:transform .15s,box-shadow .15s,border-color .15s}.lesson-card:hover{transform:translateY(-2px);border-color:#c7d2fe;box-shadow:var(--shadow)}.lesson-card .top{display:flex;align-items:center;justify-content:space-between;gap:8px;font-size:12px}.lesson-card h3{margin:0;font-size:17px}.lesson-card p{margin:0;color:var(--muted);font-size:13.5px;min-height:44px}.lesson-card .meta{display:flex;align-items:center;justify-content:space-between;color:var(--muted);font-size:12.5px;border-top:1px dashed var(--line);padding-top:10px}.lesson-header{padding:26px 28px;border-radius:var(--radius);background:#fff;border:1px solid var(--line)}.lesson-header h1{margin:8px 0 6px;font-size:26px}.lesson-header .sub{margin:0;color:var(--muted)}.lesson-body{display:grid;grid-template-columns:minmax(0,1fr);gap:20px;margin-top:20px}.md-body{padding:28px 32px;background:#fff;border:1px solid var(--line);border-radius:var(--radius);font-size:15.5px}.md-body h2{margin:28px 0 12px;padding-bottom:8px;border-bottom:1px solid var(--line);font-size:20px}.md-body h3{margin:22px 0 10px;font-size:17px;color:var(--brand-dark)}.md-body p{margin:0 0 12px}.md-body ul,.md-body ol{margin:0 0 14px;padding-left:22px}.md-body li{margin-bottom:6px}.md-body blockquote{margin:16px 0;padding:12px 16px;border-left:4px solid var(--brand);background:var(--brand-light);border-radius:0 10px 10px 0;color:var(--ink-2)}.md-body code{padding:2px 6px;border-radius:6px;background:#f3f4f6;font-size:13.5px}.md-body .md-table{overflow-x:auto;margin:14px 0 18px}.md-body table{width:100%;border-collapse:collapse;font-size:14px}.md-body th,.md-body td{padding:9px 12px;border:1px solid var(--line);text-align:left}.md-body th{background:#f8fafc;font-weight:600}.md-body hr{border:none;border-top:1px solid var(--line);margin:24px 0}.exercise{padding:20px 22px;border:1px solid var(--line);border-radius:14px;background:#fff;margin-bottom:14px}.exercise.answered-correct{border-color:#a7f3d0;background:#f6fefb}.exercise.answered-wrong{border-color:#fecaca;background:snow}.exercise-head{display:flex;align-items:center;gap:10px;margin-bottom:10px;font-size:13px;color:var(--muted)}.exercise-head .no{display:grid;place-items:center;width:26px;height:26px;border-radius:8px;background:var(--brand-light);color:var(--brand-dark);font-weight:700;font-size:13px}.exercise-prompt{font-size:15.5px;font-weight:600;margin:0 0 14px;white-space:pre-wrap}.options{display:grid;gap:8px}.option{display:flex;align-items:center;gap:10px;padding:10px 14px;border:1px solid var(--line);border-radius:10px;background:#fff;text-align:left;font-size:14.5px;transition:border-color .15s,background .15s}.option:hover:not(:disabled){border-color:var(--brand);background:#fafaff}.option.selected{border-color:var(--brand);background:var(--brand-light)}.option.correct{border-color:var(--success);background:var(--success-bg)}.option.wrong{border-color:var(--danger);background:var(--danger-bg)}.option-key{display:grid;place-items:center;width:22px;height:22px;border-radius:6px;background:#f3f4f6;font-size:12px;font-weight:700;color:var(--ink-2);flex-shrink:0}.answer-row{display:flex;gap:10px;align-items:center}.answer-input{flex:1;padding:10px 14px;border:1px solid var(--line);border-radius:10px;outline:none;transition:border-color .15s}.answer-input:focus{border-color:var(--brand);box-shadow:0 0 0 3px #4f46e51f}.feedback{margin-top:14px;padding:14px 16px;border-radius:12px;font-size:14px;border:1px solid}.feedback.correct{background:var(--success-bg);border-color:#a7f3d0;color:#14532d}.feedback.wrong{background:var(--danger-bg);border-color:#fecaca;color:#991b1b}.feedback .row{margin-top:6px}.feedback .k{font-weight:600}.exam-bar{position:sticky;top:64px;z-index:10;display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:12px;padding:12px 18px;margin-bottom:18px;border-radius:14px;background:#fff;border:1px solid var(--line);box-shadow:var(--shadow)}.countdown{font-size:18px;font-weight:700;font-variant-numeric:tabular-nums;color:var(--brand-dark)}.countdown.urgent{color:var(--danger)}.progress-track{height:8px;border-radius:999px;background:#eef0f4;overflow:hidden}.progress-track>div{height:100%;border-radius:999px;background:linear-gradient(90deg,#6366f1,#0ea5e9);transition:width .25s}.qnav{display:flex;flex-wrap:wrap;gap:6px;margin-bottom:16px}.qnav button{width:34px;height:34px;border-radius:9px;border:1px solid var(--line);background:#fff;font-size:13px;font-weight:600;color:var(--muted)}.qnav button.done{background:var(--brand-light);border-color:#c7d2fe;color:var(--brand-dark)}.qnav button.current{background:var(--brand);border-color:var(--brand);color:#fff}.result-hero{display:flex;flex-wrap:wrap;align-items:center;gap:28px;padding:28px;border-radius:var(--radius);background:#fff;border:1px solid var(--line)}.score-ring{position:relative;width:132px;height:132px;border-radius:50%;display:grid;place-items:center;background:conic-gradient(var(--brand) calc(var(--p) * 1%),#eef0f4 0)}.score-ring:after{content:"";position:absolute;top:12px;right:12px;bottom:12px;left:12px;border-radius:50%;background:#fff}.score-ring .num{position:relative;z-index:1;font-size:30px;font-weight:700;color:var(--brand-dark)}.auth-wrap{display:grid;place-items:center;padding:40px 0}.auth-card{width:100%;max-width:420px;padding:32px;border-radius:var(--radius);background:#fff;border:1px solid var(--line);box-shadow:var(--shadow)}.auth-card h1{margin:0 0 6px;font-size:22px}.auth-card .tip{margin:0 0 22px;color:var(--muted);font-size:13.5px}.field{margin-bottom:16px}.field label{display:block;margin-bottom:6px;font-size:13.5px;font-weight:600;color:var(--ink-2)}.field input{width:100%;padding:11px 14px;border:1px solid var(--line);border-radius:10px;outline:none;transition:border-color .15s,box-shadow .15s}.field input:focus{border-color:var(--brand);box-shadow:0 0 0 3px #4f46e51f}.field .hint{margin-top:6px;font-size:12.5px;color:var(--muted)}.demo-tip{margin-top:18px;padding:12px 14px;border-radius:12px;background:#f8fafc;border:1px dashed var(--line);font-size:13px;color:var(--muted)}.dash-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));gap:16px}.list-item{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:12px 0;border-bottom:1px dashed var(--line);font-size:14px}.list-item:last-child{border-bottom:none}.mistake-item{padding:16px 0;border-bottom:1px dashed var(--line)}.mistake-item:last-child{border-bottom:none}.mistake-item .q{font-weight:600;margin-bottom:6px}.mistake-item .a{font-size:13.5px;color:var(--muted)}.mistake-item .a b{color:var(--success)}@media(max-width:720px){.navbar{padding:0 16px;gap:12px}.navbar nav a{padding:8px 10px}.main{padding:20px 14px 48px}.md-body{padding:20px 18px}.hero{padding:28px 22px}.hero h1{font-size:25px}}