/* ============================================================
   layout.css —— 骨架：进度条 / 顶部导航 / 区块 / 栅格 / 页脚
   ============================================================ */

/* —— 滚动进度条 —— */
.progress {
  position: fixed; top: 0; left: 0; height: 3px; width: 0; z-index: 200;
  background: linear-gradient(90deg, var(--brand), var(--sky));
  transition: width .1s linear;
}

/* —— 顶部导航 —— */
.site-header {
  position: fixed; top: 0; left: 0; right: 0; z-index: 150;
  height: var(--nav-h); display: flex; align-items: center;
  transition: background var(--t), box-shadow var(--t), border-color var(--t);
  border-bottom: 1px solid transparent;
}
.site-header.is-stuck {
  background: rgba(255,255,255,.84);
  backdrop-filter: blur(16px) saturate(1.4);
  -webkit-backdrop-filter: blur(16px) saturate(1.4);
  border-bottom-color: var(--line);
  box-shadow: 0 6px 24px -20px rgba(13,31,22,.5);
}
.nav { width: min(var(--wrap), 92vw); margin-inline: auto; display: flex; align-items: center; gap: var(--sp-5); }

.brand { display: flex; align-items: center; gap: var(--sp-2); flex: none; }
.brand-mark {
  width: 36px; height: 36px; border-radius: 11px; display: grid; place-items: center;
  background: linear-gradient(140deg, var(--brand), #0bb3a0 55%, var(--sky));
  box-shadow: 0 6px 16px -6px rgba(18,183,106,.7);
}
.brand-mark img { width: 22px; height: 22px; }
.brand-text { font-weight: 800; font-size: 18px; letter-spacing: -.4px; line-height: 1.1; }
.brand-text small {
  display: block; font-size: 10px; font-weight: 600; letter-spacing: 2.2px;
  color: var(--muted); line-height: 1; margin-top: 3px;
}

.nav-menu { display: flex; gap: 2px; margin-left: auto; align-items: center; }
.nav-item { position: relative; }
.nav-menu a {
  padding: 8px 13px; border-radius: var(--r-sm); font-size: 14.5px;
  color: var(--ink-2); font-weight: 500; transition: var(--t-fast);
}
.nav-menu a:hover { color: var(--brand-dark); background: var(--brand-50); }
.nav-menu a.is-active { color: var(--brand-dark); background: var(--brand-50); font-weight: 600; }
.nav-trigger { padding: 8px 13px; border-radius: var(--r-sm); font-size: 14.5px; color: var(--ink-2); font-weight: 500; transition: var(--t-fast); }
.nav-trigger::after { content: '⌄'; margin-left: 6px; font-size: 12px; }
.nav-trigger:hover, .nav-item.is-open .nav-trigger { color: var(--brand-dark); background: var(--brand-50); }
.nav-dropdown { display: none; position: absolute; top: calc(100% + 8px); left: 0; min-width: 170px; padding: 7px; border: 1px solid var(--line); border-radius: var(--r-md); background: rgba(255,255,255,.98); box-shadow: var(--sh-md); z-index: 170; }
.nav-item:hover .nav-dropdown, .nav-item:focus-within .nav-dropdown, .nav-item.is-open .nav-dropdown { display: flex; flex-direction: column; }
.nav-dropdown a { display: block; white-space: nowrap; }

.nav-actions { display: flex; gap: var(--sp-2); align-items: center; }
.nav-burger { display: none; margin-left: auto; width: 40px; height: 40px; border-radius: 11px;
  border: 1px solid var(--line); background: #fff; place-items: center; }
.nav-burger span { display: block; width: 17px; height: 1.8px; background: var(--ink); border-radius: 2px; margin: 3px auto; }

/* —— 区块 —— */
.section { padding: var(--section-y) 0; position: relative; }
.section--white { background: #fff; border-block: 1px solid var(--line); }
.section--sink  { background: var(--surface-sink); }
.section-head { max-width: 780px; margin-bottom: var(--sp-7); }

/* —— 通用栅格 —— */
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: var(--sp-5); }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: var(--sp-5); }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: var(--sp-4); }

/* —— 页脚（极简一行） —— */
.site-footer { background: var(--ink); color: rgba(255,255,255,.7); border-top: 0; padding: 60px 0 30px; margin-top: var(--sp-6); }
.footer-grid { display: grid; grid-template-columns: 1.5fr 1fr 1fr 1fr; gap: 40px; margin-bottom: 40px; }
.footer-brand { display: flex; align-items: center; gap: 10px; font-weight: 700; font-size: 18px; color: #fff; margin-bottom: 16px; }
.footer-brand .brand-mark { width: 32px; height: 32px; background: #fff; }
.footer-brand .brand-mark img { width: 23px; height: 23px; }
.footer-desc { max-width: 320px; color: rgba(255,255,255,.55); font-size: 13px; line-height: 1.7; }
.footer-col h4 { color: #fff; font-size: 14px; margin-bottom: 16px; }
.footer-col ul { display: flex; flex-direction: column; gap: 10px; }
.footer-col a { color: rgba(255,255,255,.55); font-size: 13px; }
.footer-col a:hover { color: #fff; }
.footer-bottom { display: flex; justify-content: space-between; align-items: center; border-top: 1px solid rgba(255,255,255,.1); padding-top: 24px; font-size: 12px; color: rgba(255,255,255,.4); }
.footer-bottom a:hover { color: #fff; }
.footer-line { display: flex; align-items: center; gap: var(--sp-4); flex-wrap: wrap; }
.footer-line .brand-text { font-size: 15px; }
.footer-line .brand-mark { width: 30px; height: 30px; border-radius: 9px; }
.footer-line .brand-mark img { width: 18px; height: 18px; }
.footer-line nav { display: flex; gap: var(--sp-4); margin-left: auto; }
.footer-line a.f-link { font-size: 13px; color: var(--muted); transition: var(--t-fast); }
.footer-line a.f-link:hover { color: var(--brand-dark); }
.footer-copy { width: 100%; font-size: 12px; color: var(--muted); margin-top: var(--sp-3); }