/* ============================================================
   中小学AI教育 ARM基校联合体 V5.0 —— 界面设计系统
   ARM = AI（人工智能）+ Resource（资源互通）+ Management（管理协同）+ 做中学
   ============================================================ */
:root {
  /* 品牌色 */
  --brand-blue: #2B6DE8;          /* AI / 科技 */
  --brand-blue-dark: #1E52C0;
  --brand-blue-light: #EAF1FF;
  --brand-orange: #FF8A3D;        /* 做中学实践 */
  --brand-orange-dark: #E96F1F;
  --brand-orange-light: #FFF1E6;
  --brand-teal: #0EA5A4;          /* 资源互通 */
  --brand-teal-light: #E3F7F6;
  --brand-green: #22A55D;         /* 成功/离线可用 */
  --brand-red: #E5484D;

  /* 中性色 */
  --ink-900: #16203A;
  --ink-700: #2E3A55;
  --ink-500: #5B6780;
  --ink-400: #8A94AC;
  --line: #E6EAF2;
  --bg-soft: #F5F7FC;
  --bg: #FFFFFF;

  /* 字体 */
  --font: "PingFang SC", "Microsoft YaHei", "Segoe UI", -apple-system, Roboto, "Helvetica Neue", Arial, sans-serif;

  /* 阴影与圆角 */
  --radius: 16px;
  --radius-sm: 10px;
  --shadow-sm: 0 2px 8px rgba(22,32,58,.06);
  --shadow-md: 0 8px 28px rgba(22,32,58,.10);
  --shadow-lg: 0 18px 50px rgba(22,32,58,.14);
  --grad-blue: linear-gradient(135deg, #2B6DE8 0%, #5B8CFF 100%);
  --grad-orange: linear-gradient(135deg, #FF8A3D 0%, #FFB15C 100%);
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font);
  color: var(--ink-900);
  background: var(--bg-soft);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
a { text-decoration: none; color: inherit; }
img { max-width: 100%; display: block; }

/* ---------- 通用容器 ---------- */
.wrap { width: 100%; max-width: 1180px; margin: 0 auto; padding: 0 24px; }

/* ---------- 顶部导航 ---------- */
.topbar {
  position: sticky; top: 0; z-index: 100;
  background: rgba(255,255,255,.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--line);
}
.topbar-inner { display: flex; align-items: center; justify-content: space-between; height: 68px; }
.brand { display: flex; align-items: center; gap: 12px; }
.brand-logo {
  width: 42px; height: 42px; border-radius: 12px;
  background: var(--grad-blue);
  display: grid; place-items: center; color: #fff; font-weight: 800; font-size: 18px;
  box-shadow: var(--shadow-sm);
}
.brand-name { font-weight: 800; font-size: 17px; line-height: 1.2; }
.brand-sub { font-size: 11px; color: var(--ink-400); letter-spacing: .5px; }
.nav { display: flex; align-items: center; gap: 6px; }
.nav a {
  padding: 8px 14px; border-radius: 10px; font-size: 14px; font-weight: 500;
  color: var(--ink-700); transition: all .2s;
}
.nav a:hover { background: var(--bg-soft); color: var(--brand-blue); }
.nav a.active { background: var(--brand-blue-light); color: var(--brand-blue-dark); font-weight: 600; }
.nav .btn {
  background: var(--grad-blue); color: #fff; font-weight: 600;
  box-shadow: var(--shadow-sm);
}
.nav .btn:hover { background: var(--grad-blue); color: #fff; transform: translateY(-1px); }

/* ---------- 页面头部 ---------- */
.page-hero { padding: 48px 0 32px; text-align: center; }
.page-hero .badge {
  display: inline-flex; align-items: center; gap: 8px;
  background: var(--brand-blue-light); color: var(--brand-blue-dark);
  padding: 6px 16px; border-radius: 999px; font-size: 13px; font-weight: 600;
  margin-bottom: 18px;
}
.page-hero h1 { font-size: clamp(28px, 4vw, 40px); font-weight: 800; letter-spacing: -.5px; }
.page-hero p { color: var(--ink-500); font-size: 16px; margin-top: 12px; max-width: 640px; margin-left: auto; margin-right: auto; }

/* ---------- 模式切换卡片 ---------- */
.mode-switch {
  display: inline-flex; background: #fff; border: 1px solid var(--line);
  border-radius: 14px; padding: 6px; margin: 8px auto 0; gap: 6px; box-shadow: var(--shadow-sm);
}
.mode-switch a {
  display: flex; align-items: center; gap: 8px;
  padding: 10px 22px; border-radius: 10px; font-weight: 600; font-size: 14px;
  color: var(--ink-500); transition: all .2s;
}
.mode-switch a.online { color: var(--brand-blue); }
.mode-switch a.offline { color: var(--brand-teal); }
.mode-switch a.active { background: var(--ink-900); color: #fff; }
.mode-switch a.online.active { background: var(--brand-blue); }
.mode-switch a.offline.active { background: var(--brand-teal); }

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 13px 26px; border-radius: 12px; font-weight: 600; font-size: 15px;
  border: none; cursor: pointer; transition: all .2s;
}
.btn-primary { background: var(--grad-blue); color: #fff; box-shadow: 0 6px 18px rgba(43,109,232,.30); }
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 10px 24px rgba(43,109,232,.38); }
.btn-teal { background: var(--brand-teal); color: #fff; box-shadow: 0 6px 18px rgba(14,165,164,.30); }
.btn-teal:hover { transform: translateY(-2px); }
.btn-orange { background: var(--grad-orange); color: #fff; box-shadow: 0 6px 18px rgba(255,138,61,.30); }
.btn-outline { background: #fff; color: var(--brand-blue); border: 1.5px solid var(--brand-blue); }
.btn-outline:hover { background: var(--brand-blue-light); }
.btn-lg { padding: 16px 34px; font-size: 16px; }

/* ---------- 区块标题 ---------- */
.sec { padding: 44px 0; }
.sec-head { text-align: center; margin-bottom: 34px; }
.sec-tag { display: inline-block; font-size: 13px; font-weight: 700; color: var(--brand-orange-dark); letter-spacing: 1px; margin-bottom: 8px; }
.sec-title { font-size: clamp(22px, 3vw, 30px); font-weight: 800; }
.sec-desc { color: var(--ink-500); margin-top: 10px; font-size: 15px; }

/* ---------- 卡片 ---------- */
.card { background: #fff; border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow-sm); }

/* ---------- 功能标签 ---------- */
.chip {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 5px 12px; border-radius: 999px; font-size: 12.5px; font-weight: 600;
}
.chip-blue { background: var(--brand-blue-light); color: var(--brand-blue-dark); }
.chip-orange { background: var(--brand-orange-light); color: var(--brand-orange-dark); }
.chip-teal { background: var(--brand-teal-light); color: var(--brand-teal); }
.chip-green { background: #E6F7EE; color: var(--brand-green); }

/* ---------- 页脚 ---------- */
.footer { background: var(--ink-900); color: #C7CFE0; margin-top: 40px; padding: 40px 0 24px; }
.footer .grid { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 32px; }
.footer h4 { color: #fff; font-size: 15px; margin-bottom: 14px; }
.footer a { display: block; font-size: 13.5px; color: #9AA6BD; padding: 4px 0; }
.footer a:hover { color: #fff; }
.footer .copy { border-top: 1px solid rgba(255,255,255,.1); margin-top: 30px; padding-top: 20px; font-size: 12.5px; color: #7B879E; text-align: center; }
.footer .copy .arm { color: var(--brand-orange); font-weight: 700; }

/* ---------- 响应式 ---------- */
@media (max-width: 860px) {
  .nav a { padding: 6px 10px; font-size: 13px; }
  .nav .btn { display: none; }
  .footer .grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 560px) {
  .brand-sub { display: none; }
}