:root{
  --ink:#101820;--green:#0a5b4b;--teal:#0b806d;--coral:#ef5a3c;
  --paper:#f5f4ef;--white:#fff;--line:#d9ded9;--muted:#61706d;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;font-family:"Microsoft YaHei","PingFang SC",Arial,sans-serif;color:var(--ink);background:var(--paper);line-height:1.6}
a{color:inherit;text-decoration:none}
img{max-width:100%}
button,input,select,textarea{font:inherit}
.wrap{width:min(1100px,92vw);margin:0 auto}
.site-header{background:var(--green);color:#fff;padding:18px 0;position:sticky;top:0;z-index:20}
.site-header .wrap{display:flex;align-items:center;gap:18px}
.brand{display:flex;align-items:center;gap:10px;font-weight:800}
.brand-mark{width:36px;height:36px;display:grid;place-items:center;background:var(--coral);border-radius:8px}
.brand small{display:block;font-size:10px;opacity:.75;font-weight:500}
.site-header nav{margin-left:auto;display:flex;gap:18px;font-size:14px}
.site-header nav a:hover{color:var(--coral)}
.hero{padding:56px 0 28px}
.hero h1{font-size:clamp(28px,5vw,44px);line-height:1.2;margin:0 0 12px}
.hero p{color:var(--muted);max-width:640px;margin:0}
.grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:20px;padding:12px 0 48px}
@media(max-width:900px){.grid{grid-template-columns:repeat(2,minmax(0,1fr))}}
@media(max-width:580px){.grid{grid-template-columns:1fr}.site-header nav{display:none}}
.card{background:var(--white);border:1px solid var(--line);border-radius:14px;overflow:hidden;display:flex;flex-direction:column;transition:transform .15s,box-shadow .15s}
.card:hover{transform:translateY(-2px);box-shadow:0 10px 28px rgba(16,24,32,.08)}
.cover{aspect-ratio:16/10;display:flex;align-items:flex-end;padding:16px;color:#fff;position:relative}
.cover .tag{position:absolute;top:12px;left:12px;background:rgba(0,0,0,.35);padding:4px 10px;border-radius:999px;font-size:12px}
.cover h3{margin:0;font-size:20px;text-shadow:0 1px 8px rgba(0,0,0,.35)}
.card-body{padding:16px 16px 18px;display:flex;flex-direction:column;gap:10px;flex:1}
.card-body p{margin:0;color:var(--muted);font-size:13px;flex:1}
.meta{display:flex;align-items:center;justify-content:space-between;gap:10px}
.price{font-size:22px;font-weight:800;color:var(--coral)}
.price small{font-size:12px;color:var(--muted);font-weight:500}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;border:0;border-radius:10px;padding:12px 18px;font-weight:700;cursor:pointer;background:var(--coral);color:#fff}
.btn:hover{filter:brightness(1.05)}
.btn.secondary{background:#fff;color:var(--green);border:1px solid var(--line)}
.btn.wechat{background:#07c160}
.btn.alipay{background:#1677ff}
.btn.block{width:100%}
.detail{display:grid;grid-template-columns:1.1fr .9fr;gap:28px;padding:36px 0 56px}
@media(max-width:800px){.detail{grid-template-columns:1fr}}
.panel{background:#fff;border:1px solid var(--line);border-radius:14px;padding:22px}
.panel h1{margin:0 0 8px;font-size:clamp(24px,4vw,34px)}
.panel .sub{color:var(--muted);margin:0 0 16px}
.outline{margin:0;padding-left:18px}
.outline li{margin:6px 0}
.buy-box .price{font-size:32px;margin:8px 0 16px}
.pay-actions{display:grid;gap:10px}
.muted{color:var(--muted);font-size:13px}
.pay-page{max-width:520px;margin:40px auto;padding:0 4vw 60px}
.qr{background:#fff;border:1px solid var(--line);border-radius:14px;padding:24px;text-align:center}
.qr img{width:min(240px,70vw);height:auto}
.status{margin-top:14px;font-weight:700}
.lesson{background:#fff;border:1px solid var(--line);border-radius:12px;padding:18px;margin:12px 0}
.lesson h3{margin:0 0 8px}
.lesson-body{white-space:pre-wrap;color:#24302c}
.admin{max-width:960px;margin:30px auto;padding:0 4vw 60px}
.admin table{width:100%;border-collapse:collapse;background:#fff;border:1px solid var(--line)}
.admin th,.admin td{border-bottom:1px solid var(--line);padding:10px 12px;text-align:left;font-size:13px;vertical-align:top}
.admin form{display:grid;gap:10px;background:#fff;border:1px solid var(--line);border-radius:12px;padding:16px;margin:16px 0}
.admin label{display:grid;gap:4px;font-size:13px;font-weight:700}
.admin input,.admin textarea{padding:10px;border:1px solid var(--line);border-radius:8px;font-weight:400}
.flash{padding:12px 14px;border-radius:10px;background:#e8f6ef;color:var(--green);margin:12px 0}
.error{background:#fdecea;color:#a32020}
footer{border-top:1px solid var(--line);padding:28px 0 40px;color:var(--muted);font-size:13px}
footer .wrap{display:flex;flex-wrap:wrap;gap:16px;justify-content:space-between;align-items:center}
footer a{color:var(--green);text-decoration:underline}
.note{font-size:12px;color:var(--muted)}