/* 网梯直播课堂门户站样式。
 *
 * 规格量自腾讯会议官网（computed style 实测，非目测）：
 *   主标题 52px/600、字距 -1.56px —— 负字距是中文大标题精致感的来源；
 *   主按钮 #045afe、圆角 20px 全胶囊、高 40px、字号 14px；
 *   导航条 80px、透明无阴影；内容宽 1200；纯白底，分区靠极淡蓝白渐变而不是分割线。
 */
:root {
  --brand: #045afe;
  --brand-dark: #0345c8;
  --ink: #000;
  --ink-2: #4a5160;
  --ink-3: #8b93a1;
  --line: #e6e9ef;
  --panel: #fff;
  --wrap: 1200px;
  --radius: 12px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0; background: var(--panel); color: var(--ink);
  font: 16px/1.7 -apple-system, "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; text-decoration: none; }
img { max-width: 100%; display: block; }
.wrap { max-width: var(--wrap); margin: 0 auto; padding: 0 24px; }

/* ── 顶栏 ───────────────────────────────────────── */
.nav { height: 80px; display: flex; align-items: center; gap: 32px; }
.nav .logo { display: flex; align-items: center; gap: 10px; font-size: 18px; font-weight: 600; letter-spacing: -.3px; }
.nav .logo-mark {
  width: 32px; height: 32px; border-radius: 8px; flex: none;
  display: grid; place-items: center; color: #fff;
  background: linear-gradient(145deg, #2f7cf0, #174dbb);
}
.nav .logo-mark svg { width: 19px; height: 19px; }
.nav-links { display: flex; gap: 26px; font-size: 15px; color: var(--ink-2); }
.nav-links a:hover, .nav-links a.on { color: var(--brand); }
.nav-right { margin-left: auto; display: flex; align-items: center; gap: 18px; font-size: 14px; }
.nav-right .plain { color: var(--ink-2); }
.nav-right .plain:hover { color: var(--brand); }

/* 胶囊按钮。腾讯会议的主按钮是全圆角，不是 8px 小圆角 —— 这一点最影响「像不像」。 */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  height: 40px; padding: 0 20px; border-radius: 20px; border: none; cursor: pointer;
  font-size: 14px; font-family: inherit; white-space: nowrap; transition: background .15s, color .15s;
}
.btn-primary { background: var(--brand); color: #fff; }
.btn-primary:hover { background: var(--brand-dark); }
.btn-ghost { background: transparent; color: var(--ink); box-shadow: inset 0 0 0 1px var(--line); }
.btn-ghost:hover { color: var(--brand); box-shadow: inset 0 0 0 1px var(--brand); }
.btn-lg { height: 48px; padding: 0 30px; border-radius: 24px; font-size: 16px; }

/* ── 分区背景：极淡的蓝白渐变，不用分割线 ─────────── */
.tint { background: linear-gradient(180deg, #f4f8ff, #fff); }
.tint-full { background: linear-gradient(160deg, #eef4ff 0%, #f7fafe 55%, #fff 100%); }

/* ── 首屏 ───────────────────────────────────────── */
.hero { padding: 40px 0 72px; }
.hero-grid { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.15fr); gap: 56px; align-items: center; }
.hero h1 {
  margin: 0 0 18px; font-size: 52px; font-weight: 600; line-height: 68px;
  letter-spacing: -1.56px;  /* 实测腾讯会议就是这个负字距 */
}
.hero .sub { margin: 0 0 30px; font-size: 17px; color: var(--ink-2); }
.hero .acts { display: flex; gap: 14px; flex-wrap: wrap; }
.hero .note { margin: 18px 0 0; font-size: 13px; color: var(--ink-3); }
.shot { border-radius: var(--radius); overflow: hidden; box-shadow: 0 1px 2px rgba(16,24,40,.06), 0 18px 50px rgba(16,24,40,.14); }

/* ── 通用分区标题 ───────────────────────────────── */
.sec { padding: 72px 0; }
.sec-head { text-align: center; margin-bottom: 44px; }
.sec-head h2 { margin: 0 0 12px; font-size: 34px; font-weight: 600; letter-spacing: -.8px; }
.sec-head p { margin: 0; color: var(--ink-2); font-size: 16px; }

/* ── 能力卡 ─────────────────────────────────────── */
.cards { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 20px; }
.card {
  padding: 26px 24px; border-radius: var(--radius); background: var(--panel);
  box-shadow: 0 1px 2px rgba(16,24,40,.05), 0 6px 20px rgba(16,24,40,.06);
}
.card h3 { margin: 14px 0 8px; font-size: 18px; font-weight: 600; }
.card p { margin: 0; color: var(--ink-2); font-size: 14.5px; }
.card .ico { width: 44px; height: 44px; border-radius: 11px; display: grid; place-items: center; color: #fff; background: linear-gradient(145deg, #4a90f7, #1a63d8); }
.card .ico svg { width: 24px; height: 24px; }

/* ── 下载卡片阵（照腾讯会议下载中心：一排蓝色方卡）─── */
.dl-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(168px, 1fr)); gap: 16px; }
.dl-card {
  position: relative; aspect-ratio: 1 / .82; border-radius: var(--radius); overflow: hidden;
  display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 12px;
  background: linear-gradient(150deg, #3f83f4, #1155e0); color: #fff;
  transition: transform .18s, box-shadow .18s;
}
.dl-card:hover { transform: translateY(-3px); box-shadow: 0 12px 30px rgba(4,90,254,.28); }
.dl-card .os-ico { width: 56px; height: 56px; }
.dl-card .os { font-size: 16px; font-weight: 500; }
.dl-card .meta { font-size: 12px; opacity: .85; }
/* 角标：左上「推荐」等标签，右上下载图标 */
.dl-card .tag {
  position: absolute; top: 0; left: 0; padding: 3px 10px; font-size: 11px;
  border-radius: 0 0 8px 0; background: rgba(255,255,255,.22);
}
.dl-card .corner { position: absolute; top: 10px; right: 10px; width: 18px; height: 18px; opacity: .9; }
/* 还拿不到的平台：灰卡、不可点 */
.dl-card.soon { background: linear-gradient(150deg, #aeb6c4, #8d96a6); cursor: default; }
.dl-card.soon:hover { transform: none; box-shadow: none; }
/* 次要入口（网页版）用白卡 */
.dl-wide { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 16px; margin-top: 16px; }
.dl-plain {
  display: flex; align-items: center; gap: 16px; padding: 22px 24px; border-radius: var(--radius);
  background: var(--panel); box-shadow: 0 1px 2px rgba(16,24,40,.05), 0 6px 20px rgba(16,24,40,.06);
}
.dl-plain .os-ico { width: 44px; height: 44px; color: var(--brand); flex: none; }
.dl-plain strong { display: block; font-size: 16px; font-weight: 600; }
.dl-plain span { font-size: 13.5px; color: var(--ink-2); }

/* ── 页脚 ───────────────────────────────────────── */
.foot { background: #f7f9fc; padding: 48px 0 28px; margin-top: 20px; }
.foot-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 28px; }
.foot h4 { margin: 0 0 14px; font-size: 14px; font-weight: 600; }
.foot ul { margin: 0; padding: 0; list-style: none; display: grid; gap: 9px; }
.foot a { font-size: 13.5px; color: var(--ink-2); }
.foot a:hover { color: var(--brand); }
.foot-bar { margin-top: 36px; padding-top: 20px; border-top: 1px solid var(--line); font-size: 13px; color: var(--ink-3); display: flex; gap: 18px; flex-wrap: wrap; }

@media (max-width: 900px) {
  .hero-grid, .cards { grid-template-columns: minmax(0, 1fr); }
  .hero { padding: 20px 0 48px; }
  .hero h1 { font-size: 34px; line-height: 46px; letter-spacing: -.8px; }
  .sec { padding: 48px 0; }
  .sec-head h2 { font-size: 26px; }
  .nav { height: 64px; gap: 16px; }
  .nav-links { display: none; }
}