/* layout.css — 导航 / 容器 / 栅格 / 页脚 */

.shell {
  width: 100%;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 20px;
}
.shell-narrow { max-width: 820px; }

/* ---------- 顶栏 ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--nav-h);
  display: flex;
  align-items: center;
  background: var(--bg-overlay);
  backdrop-filter: saturate(1.4) blur(10px);
  -webkit-backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--line);
}
.nav-inner {
  width: 100%;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 20px;
  display: flex;
  align-items: center;
  gap: 20px;
}

.brand {
  display: flex;
  align-items: baseline;
  gap: 9px;
  color: var(--ink);
  font-weight: 600;
  letter-spacing: 0.02em;
  flex: 0 0 auto;
}
.brand:hover { text-decoration: none; }
.brand-mark {
  width: 22px; height: 22px;
  flex: 0 0 auto;
  align-self: center;
}
.brand-cn { font-size: 1rem; }
.brand-lat {
  font-family: var(--mono);
  font-size: var(--fs-tiny);
  color: var(--ink-faint);
  letter-spacing: 0.04em;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 2px;
  margin: 0;
  padding: 0;
  list-style: none;
  overflow-x: auto;
  scrollbar-width: none;
  flex: 1 1 auto;
  min-width: 0;
}
.nav-links::-webkit-scrollbar { display: none; }

.nav-links a {
  display: block;
  padding: 7px 11px;
  color: var(--ink-soft);
  font-size: var(--fs-small);
  white-space: nowrap;
  border-radius: var(--r-sm);
  transition: color var(--dur) var(--ease), background var(--dur) var(--ease);
}
.nav-links a:hover {
  color: var(--ink);
  background: var(--bg-sunken);
  text-decoration: none;
}
.nav-links a[aria-current="page"] {
  color: var(--accent);
  background: var(--re-soft);
  font-weight: 600;
}

.nav-tools {
  display: flex;
  align-items: center;
  gap: 6px;
  flex: 0 0 auto;
}

/* 桌面：.nav-links 的 flex/min-width/overflow 设计意图要作用在真 flex item 上。
 * 结构是 .nav-inner > nav[aria-label] > ul.nav-links，包装 <nav> 若留在
 * block + min-width:auto，22 个链接的 max-content（~1500px）会把整条 nav 撑出
 * 视口。把包装层转成可收缩的 flex item，ul 的 overflow-x:auto 内部滚动才生效。
 * 仅桌面（>900px）；≤900 汉堡布局不受影响。 */
@media (min-width: 901px) {
  .nav-inner > nav {
    display: flex;
    flex: 1 1 auto;
    min-width: 0;
  }
  /* 右缘渐隐：ui.js 检测"还有右侧余量"时给 .nav 挂 data-scroll-more；
   * 滚到底属性消失、渐隐解除，提示"到头了"。mask 只作用于渲染盒，不吃点击。 */
  .nav[data-scroll-more] .nav-links {
    -webkit-mask-image: linear-gradient(to right, #000 calc(100% - 30px), rgba(0, 0, 0, 0));
    mask-image: linear-gradient(to right, #000 calc(100% - 30px), rgba(0, 0, 0, 0));
  }
}

/* 移动端汉堡 */
.nav-toggle {
  display: none;
  width: 36px; height: 36px;
  align-items: center;
  justify-content: center;
  padding: 0;
  background: transparent;
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  color: var(--ink-soft);
  cursor: pointer;
}
.nav-toggle span {
  display: block;
  width: 15px; height: 1.5px;
  background: currentColor;
  position: relative;
  transition: background var(--dur) var(--ease);
}
.nav-toggle span::before,
.nav-toggle span::after {
  content: "";
  position: absolute;
  left: 0;
  width: 15px; height: 1.5px;
  background: currentColor;
  transition: transform var(--dur) var(--ease);
}
.nav-toggle span::before { top: -5px; }
.nav-toggle span::after  { top: 5px; }
.nav-toggle[aria-expanded="true"] span { background: transparent; }
.nav-toggle[aria-expanded="true"] span::before { transform: translateY(5px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] span::after  { transform: translateY(-5px) rotate(-45deg); }

@media (max-width: 900px) {
  .nav { height: auto; }
  .nav-inner { flex-wrap: wrap; padding-top: 10px; padding-bottom: 10px; }
  .nav-toggle { display: flex; order: 3; }
  .nav-tools { order: 2; margin-left: auto; }
  .nav-links {
    order: 4;
    flex-basis: 100%;
    display: none;
    flex-direction: column;
    align-items: stretch;
    gap: 1px;
    padding: 8px 0 4px;
    overflow: visible;
  }
  .nav[data-open="true"] .nav-links { display: flex; }
  .nav-links a { padding: 10px 12px; font-size: var(--fs-body); }
}

/* ---------- 主区域 ---------- */
main { display: block; }

.section { padding: 52px 0; }
.section-tight { padding: 32px 0; }
.section + .section { border-top: 1px solid var(--line); }

.section-head {
  margin-bottom: 24px;
  max-width: 68ch;
}
.section-head .kicker {
  display: block;
  margin-bottom: 8px;
  font-family: var(--mono);
  font-size: var(--fs-tiny);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.section-head h2 { margin-bottom: 6px; }
.section-head p { color: var(--ink-mute); margin: 0; }

/* ---------- 栅格 ---------- */
.grid { display: grid; gap: var(--gap); }
.grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }

@media (max-width: 900px) {
  .grid-4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid-3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 620px) {
  .grid-4, .grid-3, .grid-2 { grid-template-columns: minmax(0, 1fr); }
  .section { padding: 36px 0; }
}

/* 主从布局：画布 + 侧栏 */
.split {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 340px;
  gap: var(--gap-lg);
  align-items: start;
}
.split-wide { grid-template-columns: minmax(0, 1fr) 400px; }
@media (max-width: 1000px) {
  .split, .split-wide { grid-template-columns: minmax(0, 1fr); }
}

.stack { display: flex; flex-direction: column; gap: var(--gap); }
.stack-sm { gap: 10px; }
.row { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.row-between { display: flex; gap: 10px; align-items: center; justify-content: space-between; flex-wrap: wrap; }

/* ---------- 页脚 ---------- */
.footer {
  border-top: 1px solid var(--line);
  background: var(--bg-sunken);
  padding: 32px 0;
  margin-top: 40px;
}
.footer-inner {
  display: flex;
  gap: 24px;
  align-items: flex-start;
  justify-content: space-between;
  flex-wrap: wrap;
}
.footer-note {
  color: var(--ink-mute);
  font-size: var(--fs-small);
  max-width: 46ch;
}
.footer-links {
  display: flex;
  gap: 18px;
  list-style: none;
  margin: 0; padding: 0;
  font-size: var(--fs-small);
}
.footer-links a { color: var(--ink-soft); }
.footer-links a:hover { color: var(--accent); }
.footer-meta {
  width: 100%;
  padding-top: 16px;
  margin-top: 4px;
  border-top: 1px solid var(--line);
  font-family: var(--mono);
  font-size: var(--fs-tiny);
  color: var(--ink-faint);
  display: flex;
  gap: 16px;
  justify-content: space-between;
  flex-wrap: wrap;
}