/* 信奥学园 - 简洁教学风,机房低配显示器友好 */
* { box-sizing: border-box; }
body {
  margin: 0; font-family: "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  color: #1e293b; background: #f8fafc; line-height: 1.6;
}
nav {
  display: flex; gap: 18px; align-items: center; padding: 10px 24px;
  background: #0f172a; color: #e2e8f0; position: sticky; top: 0; z-index: 10;
}
nav a { color: #cbd5e1; text-decoration: none; font-size: 15px; }
nav a:hover { color: #fff; }
nav .brand { font-weight: 700; font-size: 18px; color: #fff; margin-right: 12px; }
nav .spacer { flex: 1; }
nav .who { color: #94a3b8; font-size: 14px; }
main { max-width: 1080px; margin: 0 auto; padding: 24px 20px 60px; }
footer { text-align: center; color: #94a3b8; font-size: 13px; padding: 24px; }
h1 { font-size: 26px; } h2 { font-size: 20px; margin-top: 24px; }
a { color: #2563eb; }
.error { color: #dc2626; background: #fef2f2; padding: 8px 12px; border-radius: 6px; }
.muted { color: #94a3b8; font-size: 14px; }
.tag { background: #e0f2fe; color: #0369a1; font-size: 12px; padding: 2px 8px; border-radius: 10px; margin-left: 6px; }
.badge { color: #fff; font-size: 13px; padding: 2px 10px; border-radius: 10px; font-weight: 600; }

.hero { text-align: center; padding: 48px 0 32px; }
.hero h1 { font-size: 34px; margin-bottom: 4px; }
.hero .hi { color: #475569; }
.btn, .btn-primary {
  display: inline-block; padding: 8px 18px; border-radius: 8px; border: 1px solid #cbd5e1;
  background: #fff; color: #1e293b; cursor: pointer; font-size: 15px; text-decoration: none;
}
.btn-primary { background: #2563eb; border-color: #2563eb; color: #fff; }
.btn-primary:hover { background: #1d4ed8; }
.btn.big, .btn-primary.big { padding: 12px 28px; font-size: 17px; margin: 0 6px; }
.btn-small { padding: 2px 10px; font-size: 12px; border-radius: 6px; border: 1px solid #cbd5e1; background: #fff; cursor: pointer; }

.card {
  background: #fff; border: 1px solid #e2e8f0; border-radius: 12px; padding: 20px 24px; margin: 16px 0;
}
.card.narrow { max-width: 420px; margin: 40px auto; }
.notice { background: #fffbeb; border-color: #fcd34d; }
.grid { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.split { display: grid; grid-template-columns: 1.4fr 1fr; gap: 20px; align-items: start; }
@media (max-width: 760px) { .grid, .split { grid-template-columns: 1fr; } }
a.card { text-decoration: none; color: inherit; }
a.card:hover { border-color: #2563eb; }

.list { list-style: none; padding: 0; margin: 8px 0; }
.list li { padding: 7px 0; border-bottom: 1px dashed #e2e8f0; display: flex; justify-content: space-between; align-items: center; gap: 8px; }
.list li:last-child { border-bottom: none; }

table { width: 100%; border-collapse: collapse; background: #fff; border-radius: 10px; overflow: hidden; margin-top: 12px; }
th, td { padding: 10px 14px; text-align: left; border-bottom: 1px solid #e2e8f0; font-size: 14px; }
th { background: #f1f5f9; font-weight: 600; }

label { display: block; margin: 12px 0; font-size: 14px; color: #475569; }
input:not([type=checkbox]), select, textarea {
  width: 100%; padding: 9px 12px; margin-top: 4px; border: 1px solid #cbd5e1;
  border-radius: 8px; font-size: 15px; font-family: inherit;
}
textarea { font-family: ui-monospace, Consolas, monospace; }
.row { display: flex; gap: 12px; } .row label { flex: 1; }
button.btn-primary { margin-top: 10px; }

pre {
  background: #0f172a; color: #e2e8f0; padding: 12px 14px; border-radius: 8px;
  overflow-x: auto; font-size: 14px; line-height: 1.5;
}
pre.code { background: #f1f5f9; color: #0f172a; border: 1px solid #e2e8f0; }
.sample pre { background: #f8fafc; color: #0f172a; border: 1px dashed #cbd5e1; padding: 8px 12px; }
.sample h3 { margin: 14px 0 4px; font-size: 14px; color: #64748b; }
.md h2, .md h3 { border-bottom: 1px solid #e2e8f0; padding-bottom: 4px; }
.md code { background: #eef2ff; color: #3730a3; padding: 1px 6px; border-radius: 4px; }
.md pre code { background: none; color: inherit; }
details summary { cursor: pointer; color: #2563eb; font-size: 13px; }
.lessons a { font-size: 16px; }