:root{--bg: #fff8ee;--card: #ffffff;--ink: #3a3a3a;--ink-soft: #77736b;--brand: #ff8a3d;--brand-dark: #e06f1f;--line: #f0e6d8;--radius: 20px;--radius-sm: 14px;--shadow: 0 6px 24px rgba(255, 138, 61, .1);--font: "Microsoft YaHei", "PingFang SC", "Noto Sans SC", sans-serif}*{box-sizing:border-box}html,body{margin:0;padding:0;background:var(--bg);color:var(--ink);font-family:var(--font);font-size:18px;line-height:1.75;-webkit-font-smoothing:antialiased}h1,h2,h3{line-height:1.35;font-weight:700}a{color:inherit;text-decoration:none}.top-nav{display:flex;align-items:center;gap:16px;padding:14px 24px;background:var(--card);border-bottom:2px solid var(--line);position:sticky;top:0;z-index:10}.top-nav .logo{font-size:22px;font-weight:700;color:var(--brand-dark);display:flex;align-items:center;gap:8px}.top-nav .logo .star{font-size:26px}.top-nav .nav-links{margin-left:auto;display:flex;gap:20px;font-size:18px;font-weight:600;color:var(--ink-soft)}.top-nav .nav-links a:hover{color:var(--brand-dark)}.page{max-width:1040px;margin:0 auto;padding:28px 20px 60px}.hero{background:linear-gradient(135deg,#ffe3c2,#ffd9a8);border-radius:var(--radius);padding:36px 32px;margin-bottom:28px}.hero h1{font-size:34px;margin:0 0 8px;color:#7c3e00}.hero p{margin:0;font-size:19px;color:#8a5a22}.grid-subjects{display:grid;grid-template-columns:repeat(auto-fill,minmax(210px,1fr));gap:18px;margin-top:16px}.course-card{background:var(--card);border-radius:var(--radius);overflow:hidden;box-shadow:var(--shadow);transition:transform .15s ease;border:1px solid var(--line)}.course-card:hover{transform:translateY(-4px)}.course-card .bar{height:14px}.course-card .body{padding:18px 18px 20px}.course-card .name{font-size:22px;font-weight:700;margin:0 0 4px}.course-card .desc{font-size:15px;color:var(--ink-soft);margin:0}.grid-lessons{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:18px;margin-top:16px}.lesson-card{background:var(--card);border-radius:var(--radius-sm);padding:20px;border:1px solid var(--line);box-shadow:var(--shadow);transition:transform .15s ease}.lesson-card:hover{transform:translateY(-4px)}.lesson-card h3{margin:0 0 6px;font-size:20px}.lesson-card p{margin:0 0 10px;font-size:15px;color:var(--ink-soft)}.lesson-card .tag{display:inline-block;font-size:13px;color:var(--brand-dark);background:#fff1e0;border-radius:999px;padding:2px 12px}.section-title{font-size:24px;margin:34px 0 4px}.section-sub{color:var(--ink-soft);font-size:16px;margin:0 0 8px}.lesson-detail .meta{color:var(--ink-soft);font-size:15px;margin:6px 0 20px}.reader-body{background:var(--card);border-radius:var(--radius);padding:28px 30px;border:1px solid var(--line)}.reader-body h2{font-size:24px;margin-top:28px}.reader-body p{font-size:19px}.reader-body img{max-width:100%;border-radius:var(--radius-sm)}.btn{display:inline-flex;align-items:center;gap:8px;border:none;border-radius:999px;padding:10px 22px;font-size:17px;font-weight:600;cursor:pointer;font-family:var(--font);transition:background .15s ease,transform .1s ease}.btn:active{transform:scale(.97)}.btn-primary{background:var(--brand);color:#fff}.btn-primary:hover{background:var(--brand-dark)}.btn-soft{background:#fff1e0;color:var(--brand-dark)}.btn-soft:hover{background:#ffe3c2}.bili-wrap{position:relative;aspect-ratio:16 / 9;border-radius:var(--radius-sm);overflow:hidden;margin:20px 0;background:#000}.bili-wrap iframe{position:absolute;inset:0;width:100%;height:100%;border:0}.ask-hero{background:linear-gradient(135deg,#d8f3ff,#c2ecff);border-radius:var(--radius);padding:30px;margin-bottom:24px}.ask-hero h1{margin:0 0 6px;color:#075e8a;font-size:30px}.ask-hero p{margin:0;color:#2c7aa5;font-size:17px}.topic-cards{display:flex;flex-wrap:wrap;gap:10px;margin-bottom:18px}.topic-cards button{border:2px solid #bfe6f7;background:#fff;border-radius:999px;padding:8px 18px;font-size:16px;cursor:pointer;font-family:var(--font);color:#0a6ea8;transition:background .15s ease}.topic-cards button:hover{background:#e8f7ff}.ask-input-row{display:flex;gap:10px;margin-bottom:18px;flex-wrap:wrap}.ask-input-row input{flex:1;min-width:220px;border:2px solid var(--line);border-radius:999px;padding:12px 22px;font-size:18px;font-family:var(--font);outline:none}.ask-input-row input:focus{border-color:var(--brand)}.ask-reply{background:var(--card);border-radius:var(--radius);padding:24px 28px;border:1px solid var(--line);min-height:90px;font-size:19px;white-space:pre-wrap}.ask-reply .loading{color:var(--ink-soft)}.ask-actions{margin-top:14px;display:flex;gap:10px;flex-wrap:wrap}.hint{color:var(--ink-soft);font-size:14px;margin-top:12px}.footer{text-align:center;color:#b8a88f;font-size:14px;padding:30px 0 40px}@media(max-width:640px){body{font-size:17px}.hero h1{font-size:27px}.top-nav{padding:12px 16px}.reader-body{padding:20px}}