:root {
  --bg: #0f1115;
  --panel: #171a21;
  --panel-2: #1e222b;
  --text: #e6e8ec;
  --muted: #9aa0aa;
  --line: #2a2f3a;
  --brand: #4c8dff;
  --brand-2: #2b6fe0;
  --ok: #2ec27e;
  --warn: #f0a830;
  --err: #ef5350;
  --radius: 10px;
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Microsoft YaHei", sans-serif;
  line-height: 1.6;
  font-size: 15px;
}
a { color: var(--brand); text-decoration: none; }
a:hover { text-decoration: underline; }
.container { max-width: 1080px; margin: 0 auto; padding: 0 20px; }
header.topbar {
  border-bottom: 1px solid var(--line);
  background: var(--panel);
  position: sticky; top: 0; z-index: 20;
}
.topbar .container { display: flex; align-items: center; justify-content: space-between; height: 58px; }
.brand { font-weight: 700; font-size: 18px; color: var(--text); }
.brand span { color: var(--brand); }
.nav { display: flex; gap: 18px; align-items: center; }
.nav a { color: var(--muted); }
.nav a.active, .nav a:hover { color: var(--text); text-decoration: none; }
.btn {
  display: inline-flex; align-items: center; justify-content: center;
  border: 1px solid var(--line); background: var(--panel-2); color: var(--text);
  padding: 9px 16px; border-radius: var(--radius); cursor: pointer; font-size: 14px;
  transition: .15s ease;
}
.btn:hover { border-color: var(--brand); }
.btn.primary { background: var(--brand); border-color: var(--brand); color: #fff; }
.btn.primary:hover { background: var(--brand-2); }
.btn.ghost { background: transparent; }
.btn.block { width: 100%; }
.btn:disabled { opacity: .55; cursor: not-allowed; }
.card {
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 18px;
}
.grid { display: grid; gap: 18px; }
.grid.courses { grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); }
.course-cover {
  height: 140px; border-radius: 8px; background: linear-gradient(135deg, #243049, #1a2030);
  display: flex; align-items: center; justify-content: center; color: var(--muted); font-size: 13px;
}
.course-title { font-weight: 600; margin: 12px 0 4px; }
.course-meta { color: var(--muted); font-size: 13px; }
.price { color: var(--brand); font-weight: 700; }
.section { padding: 32px 0; }
h1, h2, h3 { margin: 0 0 14px; }
.muted { color: var(--muted); }
.row { display: flex; gap: 12px; align-items: center; }
.spread { display: flex; justify-content: space-between; align-items: center; }
.field { margin-bottom: 14px; }
label { display: block; font-size: 13px; color: var(--muted); margin-bottom: 6px; }
input[type=text], input[type=email], input[type=password], input[type=number] {
  width: 100%; padding: 10px 12px; border-radius: 8px; border: 1px solid var(--line);
  background: var(--panel-2); color: var(--text); font-size: 14px; outline: none;
}
input:focus { border-color: var(--brand); }
.captcha-box { display: flex; gap: 10px; align-items: center; }
.captcha-box img { border-radius: 6px; cursor: pointer; border: 1px solid var(--line); height: 42px; }
.msg { padding: 10px 12px; border-radius: 8px; font-size: 13px; margin-bottom: 12px; display: none; }
.msg.err { background: rgba(239,83,80,.12); color: var(--err); display: block; }
.msg.ok { background: rgba(46,194,126,.12); color: var(--ok); display: block; }
.center-box { max-width: 420px; margin: 60px auto; }
.pill { display: inline-block; padding: 2px 10px; border-radius: 999px; font-size: 12px; background: var(--panel-2); border: 1px solid var(--line); color: var(--muted); }
.table { width: 100%; border-collapse: collapse; }
.table th, .table td { text-align: left; padding: 10px 12px; border-bottom: 1px solid var(--line); font-size: 14px; }
.table th { color: var(--muted); font-weight: 600; }
.tabs { display: flex; gap: 8px; margin-bottom: 16px; }
.tabs .tab { padding: 8px 14px; border-radius: 8px; border: 1px solid var(--line); cursor: pointer; color: var(--muted); }
.tabs .tab.active { color: var(--text); border-color: var(--brand); background: var(--panel-2); }
.lessons li { list-style: none; padding: 12px; border: 1px solid var(--line); border-radius: 8px; margin-bottom: 8px; display: flex; justify-content: space-between; align-items: center; }
.lessons { padding: 0; margin: 0; }
.hero { padding: 56px 0 30px; }
.hero h1 { font-size: 30px; }
.banner { background: var(--panel-2); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px; color: var(--muted); font-size: 14px; }
footer { border-top: 1px solid var(--line); padding: 22px 0; color: var(--muted); font-size: 13px; }

/* 运营后台 */
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: 14px; margin-bottom: 28px; }
.stat { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px; }
.stat .num { font-size: 26px; font-weight: 700; }
.stat .lab { color: var(--muted); font-size: 13px; margin-top: 4px; }
.panel { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); padding: 20px; margin-bottom: 24px; }
.codes { background: var(--panel-2); border: 1px solid var(--line); border-radius: 8px; padding: 12px; max-height: 220px; overflow: auto; white-space: pre-wrap; word-break: break-all; font-size: 13px; color: var(--muted); }
.tag { display: inline-block; padding: 1px 8px; border-radius: 6px; font-size: 12px; }
.tag.locked { background: rgba(239,83,80,.15); color: var(--err); }
.tag.active { background: rgba(46,194,126,.15); color: var(--ok); }
.tag.used { background: rgba(46,194,126,.12); color: var(--ok); }
.tag.unused { background: rgba(154,160,170,.15); color: var(--muted); }
.tag.revoked { background: rgba(240,168,48,.15); color: var(--warn); }
.admin-tools { display: flex; gap: 10px; flex-wrap: wrap; align-items: flex-end; }
.admin-tools .field { margin-bottom: 0; }
.inline-form { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }