/* ════════════════════════════════════════════════════════════════
   包租公 · 共享顶部导航 nav.css — 全站唯一来源
   引用页：intro.html（首页）/ learn.html + 全部知识库文章页（经 learn.css 同级 link）
            / calc.html（计算器）。app(index.html) 不引本文件（自带底部 nav）。
   规则：任何 <nav> 的样式只在这里改，不要再往各页内联 / learn.css 里复制一份。
   依赖各页 :root 已定义的 token：--bg --text --muted --line --line-2 --accent --accent-2。
   ════════════════════════════════════════════════════════════════ */

/* 预留滚动条槽 —— 有/无滚动条的页面之间视口同宽，导航不左右跳。
   ⚠️ scrollbar-gutter 单用不够：html overflow-y 为 visible（learn 系列默认）或旧 Safari(<18.2)
   下它不生效，短页/长页之间仍差一条滚动条宽 → 跨页切换 nav 左右跳几像素。
   叠加 overflow-y:scroll 强制 html 成为 y 滚动容器、滚动条始终占位（双保险，全浏览器同宽）。 */
html { scrollbar-gutter: stable; overflow-y: scroll; }

nav {
  position: sticky; top: 0; z-index: 100;
  padding: 18px max(24px, 5vw);
  /* 琉璃 2.0：真玻璃 chrome（对角高光 + tint + 折光），/design-system 为准 */
  background:
    linear-gradient(135deg, rgba(255,255,255,0.05), rgba(255,255,255,0.01) 45%, rgba(255,255,255,0) 70%),
    rgba(8,10,18,0.55);
  backdrop-filter: blur(20px) saturate(1.7);
  -webkit-backdrop-filter: blur(20px) saturate(1.7);
  border-bottom: 1px solid transparent;
  display: flex; justify-content: space-between; align-items: center;
  transition: border-color 0.2s, box-shadow 0.2s;
  /* 显式锁定字体（值 = canonical --font-text，硬编码防各页 token 未定义时漂移） —— 导航文字宽度跨页一致 */
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", "PingFang SC", "Microsoft YaHei", "Noto Sans SC", sans-serif;
}
nav.scrolled {
  border-bottom-color: var(--line);
  box-shadow: inset 0 1px 0 rgba(255,255,255,0.06), 0 8px 28px -12px rgba(1,3,9,0.55);
}
@supports not ((backdrop-filter: blur(1px)) or (-webkit-backdrop-filter: blur(1px))) {
  nav { background: rgba(8,10,18,0.97); }
}
@media (prefers-reduced-transparency: reduce) {
  nav { backdrop-filter: none; -webkit-backdrop-filter: none; background: rgba(8,10,18,0.97); }
}

nav .logo {
  font-size: 15px; font-weight: 600; letter-spacing: -0.01em;
  color: var(--text); text-decoration: none;
  display: flex; align-items: center; gap: 8px;
}
nav .logo .glyph {
  width: 22px; height: 22px;
  display: inline-flex; align-items: center; justify-content: center;
  color: var(--accent);
}
nav .logo .glyph svg { width: 100%; height: 100%; display: block; }

nav .nav-center { display: flex; align-items: center; flex-wrap: wrap; gap: 26px; min-width: 0; }
nav .navlink { font-size: 14px; font-weight: 500; color: var(--muted); text-decoration: none; transition: color 0.15s; white-space: nowrap; }
nav .navlink:hover { color: var(--accent); }

nav .right { display: flex; align-items: center; gap: 14px; flex-shrink: 0; }

/* 语言三段 · 分段药丸 + 选中段金渐变浮起（参考款，与 app 头一致）
   注：--accent-light 仅 app 定义，落地页未定义 → var() 回退到纯 --accent（实色金，仍带浮起感） */
nav .lang-pills { display: inline-flex; align-items: center; gap: 2px; border: 1px solid var(--line); border-radius: 999px; height: 32px; padding: 3px; background: rgba(3,5,12,0.34); box-shadow: inset 0 1.5px 4px rgba(0,0,0,0.25); }
nav .lang-pills button {
  background: transparent; border: none; padding: 0 10px;
  font-size: 12px; font-weight: 600; color: var(--muted); cursor: pointer;
  font-family: inherit; letter-spacing: 0.02em; min-width: 32px;
  height: 26px; border-radius: 999px;
  display: inline-flex; align-items: center; justify-content: center;
  transition: color 0.15s, background 0.15s;
}
nav .lang-pills button:hover { color: var(--text); }
nav .lang-pills button.active {
  background: linear-gradient(180deg, var(--accent-light, var(--accent)), var(--accent));
  color: #1A1407; font-weight: 700;
  box-shadow: 0 1px 2px rgba(0,0,0,0.28), inset 0 1px 0 rgba(255,255,255,0.45);
}

nav .calc-link {
  font-size: 13px; font-weight: 500; color: var(--accent);
  border: 1px solid rgba(232,188,114,0.32); padding: 7px 13px; border-radius: 999px;
  background: rgba(232,188,114,0.08);
  text-decoration: none; transition: background 0.15s, color 0.15s, transform 0.15s;
  display: inline-flex; align-items: center; gap: 7px; white-space: nowrap; line-height: 1;
}
nav .calc-link:hover { background: rgba(232,188,114,0.15); transform: translateY(-1px); }
nav .calc-link .calc-text { display: inline-block; }

/* 琉璃 2.0：进入应用 = 实金胶囊（一屏唯一的「确定」） */
nav .cta {
  font-size: 13px; font-weight: 600; color: #211402; white-space: nowrap;
  background: linear-gradient(160deg, #F4D292 -12%, #E6B86A 40%, #C08F3D 118%);
  padding: 8px 16px; border-radius: 999px; text-decoration: none;
  box-shadow: inset 0 1px 0 rgba(255,255,255,0.48), inset 0 -1px 0 rgba(60,30,0,0.14), 0 4px 14px -5px rgba(214,166,86,0.45);
  transition: filter 0.15s, transform 0.15s, box-shadow 0.15s;
}
nav .cta:hover {
  filter: brightness(1.06); transform: translateY(-1px);
  box-shadow: inset 0 1px 0 rgba(255,255,255,0.48), inset 0 -1px 0 rgba(60,30,0,0.14), 0 8px 20px -6px rgba(214,166,86,0.58);
}

/* 汉堡按钮（由 nav.js 注入；桌面隐藏，仅手机 + .js-nav 显示）—— 三道横线 → X 形变 */
nav .nav-ham {
  display: none; flex: 0 0 36px; width: 36px; height: 36px; padding: 0;
  flex-direction: column; align-items: center; justify-content: center;
  border: 1px solid var(--line-2); border-radius: 10px;
  background: rgba(255,255,255,0.04); color: var(--text); cursor: pointer;
}
nav .nav-ham span {
  display: block; width: 17px; height: 2px; border-radius: 2px; background: currentColor;
  transition: transform 0.22s cubic-bezier(0.22,0.8,0.36,1), opacity 0.15s;
}
nav .nav-ham span + span { margin-top: 4px; }

/* ════════════════════════════════════════════════════════════════
   收纳到汉堡 —— 由内容自动触发（2026-06-16 用户选「按内容自动收纳」）
   nav.js 实时测量导航链接放不放得下：放不下就给 <nav> 加 .is-collapsed。
   不绑定具体断点 → 与语言/字号/链接数无关（EN 长文案在更宽处就收，
   中文在更窄处才收，将来加链接也自适应）。
   收起态 = 单行（logo + 进入应用 + ☰），链接/语言/Demo 收进抽屉。
   无 JS / nav.js 未跑 → nav 拿不到 .js-nav → 走下面 @media ≤880 的三行栅格兜底。
   ════════════════════════════════════════════════════════════════ */
nav.js-nav.is-collapsed { flex-wrap: wrap; gap: 10px; }
nav.js-nav.is-collapsed .logo { order: 1; flex: 1 1 auto; min-width: 0; }
nav.js-nav.is-collapsed .right { display: contents; }
nav.js-nav.is-collapsed .right .cta { order: 2; flex: 0 0 auto; }
nav.js-nav.is-collapsed .nav-ham { display: flex; order: 3; }
/* 抽屉内容默认收起 */
nav.js-nav.is-collapsed .nav-center,
nav.js-nav.is-collapsed .right .lang-pills,
nav.js-nav.is-collapsed .right .calc-link { display: none; }
/* 点开汉堡 → 手风琴展开（撑高 nav 本体，全在玻璃面板上） */
nav.js-nav.is-collapsed.menu-open .nav-center {
  display: flex; flex-direction: column; align-items: flex-start; gap: 2px;
  order: 4; flex-basis: 100%; width: 100%;
  border-top: 1px solid var(--line); margin-top: 11px; padding-top: 8px;
}
nav.js-nav.is-collapsed.menu-open .nav-center .navlink { padding: 10px 2px; width: 100%; }
nav.js-nav.is-collapsed.menu-open .right .lang-pills { display: inline-flex; order: 5; margin-top: 2px; }
nav.js-nav.is-collapsed.menu-open .right .calc-link { display: inline-flex; order: 6; margin-top: 2px; }
/* 汉堡 → X */
nav.js-nav.is-collapsed.menu-open .nav-ham span:nth-child(1) { transform: translateY(6px) rotate(45deg); }
nav.js-nav.is-collapsed.menu-open .nav-ham span:nth-child(2) { opacity: 0; }
nav.js-nav.is-collapsed.menu-open .nav-ham span:nth-child(3) { transform: translateY(-6px) rotate(-45deg); }

/* ≤880px：手机断点 —— 收紧内边距（收起态由 JS 管）+ 无 JS 三行栅格兜底 */
@media (max-width: 880px) {
  nav { padding: 12px 18px; }
  nav .lang-pills button { padding: 0 8px; min-width: 28px; }
  /* 无 JS 兜底：nav.js 没加载时保留三行栅格，仍可用 */
  nav:not(.js-nav) {
    display: grid;
    grid-template-columns: 1fr auto;
    grid-template-rows: auto auto;
    column-gap: 12px; row-gap: 10px; align-items: center;
  }
  nav:not(.js-nav) .logo { grid-column: 1; grid-row: 1; min-width: 0; }
  nav:not(.js-nav) .right { display: contents; }
  nav:not(.js-nav) .right .cta { grid-column: 2; grid-row: 1; justify-self: end; }
  nav:not(.js-nav) .right .lang-pills { grid-column: 1; grid-row: 2; justify-self: start; }
  nav:not(.js-nav) .right .calc-link { grid-column: 2; grid-row: 2; justify-self: end; }
  nav:not(.js-nav) .nav-center { grid-column: 1 / -1; grid-row: 3; gap: 16px 18px; flex-wrap: wrap; border-top: 1px solid var(--line); padding-top: 9px; }
}

/* ════════════════════════════════════════════════════════════════
   白天主题：真玻璃 nav 翻浅。仅 :root[data-theme="light"] 作用域 —— 学习站经
   learn.js / 各页 <head> 脚本设置该属性；intro.html 不设 data-theme，故首页 nav 不受影响。
   token（--text/--muted/--accent…）已由各页 :root[data-theme=light] 翻好，这里只补
   nav 自身硬编码的暗玻璃底 + 实金 CTA。
   ════════════════════════════════════════════════════════════════ */
:root[data-theme="light"] nav {
  background:
    linear-gradient(135deg, rgba(255,255,255,0.55), rgba(255,255,255,0.12) 45%, rgba(255,255,255,0) 70%),
    rgba(255,255,255,0.70);
}
:root[data-theme="light"] nav.scrolled {
  box-shadow: inset 0 1px 0 rgba(255,255,255,0.7), 0 8px 28px -12px rgba(45,40,25,0.18);
}
:root[data-theme="light"] nav .nav-ham { background: rgba(40,38,28,0.05); }
:root[data-theme="light"] nav .cta {
  background: linear-gradient(180deg, #F8DA98 0%, #E9B85E 46%, #C9923A 100%);
  color: #2A1B02;
}
@supports not ((backdrop-filter: blur(1px)) or (-webkit-backdrop-filter: blur(1px))) {
  :root[data-theme="light"] nav { background: rgba(250,250,248,0.98); }
}
@media (prefers-reduced-transparency: reduce) {
  :root[data-theme="light"] nav { background: rgba(250,250,248,0.98); }
}