/* =========================================================
   小鸟平台 · 共享外壳样式  /assets/site.css
   顺序：变量 → reset → 中文排版 → 外壳外壳 → 组件 → 响应式
   ========================================================= */

:root{
  --lake-deep:#0F3F63;
  --lake:#1F79B7;
  --lake-soft:#DCEBF6;
  --lake-tint:#EEF5FB;
  --grass:#477F55;
  --grass-soft:#E7F0E7;
  --gold:#D9A63C;
  --red:#C0523F;
  --amber:#C86A22;
  --ink:#182430;
  --ink-soft:#3C4C59;
  --mist:#66757F;
  --paper:#F7F8F6;
  --white:#FFFFFF;
  --line:rgba(15,63,99,.14);
  --line-soft:rgba(15,63,99,.08);
  --radius-s:6px;
  --radius-m:14px;
  --radius-l:28px;
  --shell:1180px;
  --gutter:20px;
  --font-display:"PingFang SC","Hiragino Sans GB","Noto Sans SC","Source Han Sans SC","Microsoft YaHei",system-ui,sans-serif;
  --font-body:"PingFang SC","Noto Sans SC","Microsoft YaHei",system-ui,-apple-system,"Segoe UI",sans-serif;
  --font-mono:ui-monospace,SFMono-Regular,Menlo,Consolas,"Noto Sans Mono CJK SC","Courier New",monospace;
  --ease:cubic-bezier(.2,.7,.2,1);
  --t-fast:160ms;
  --t-mid:220ms;
  --t-fold:260ms;
}
@media (min-width:720px){:root{--gutter:40px}}
@media (min-width:1120px){:root{--gutter:64px}}

/* ---------- reset ---------- */
*,*::before,*::after{box-sizing:border-box}
html{
  -webkit-text-size-adjust:100%;
  scroll-behavior:smooth;
  scroll-padding-top:120px;
}
body{
  margin:0;
  color:var(--ink);
  background-color:var(--paper);
  background-image:radial-gradient(rgba(15,63,99,.055) .7px,transparent .8px);
  background-size:5px 5px;
  font-family:var(--font-body);
  font-size:16.5px;
  line-height:1.75;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
img,svg{max-width:100%;height:auto}
button{font:inherit;color:inherit}
[hidden]{display:none !important}

/* ---------- 中文排版基线 ---------- */
h1,h2,h3,h4{
  margin:0 0 .6em;
  font-family:var(--font-display);
  font-weight:800;
  letter-spacing:.01em;
  line-height:1.28;
  color:var(--lake-deep);
}
h1{font-size:clamp(28px,4.6vw,52px)}
h2{font-size:clamp(24px,3.4vw,40px)}
h3{font-size:clamp(19px,2.2vw,24px)}
p{margin:0 0 1.1em}
ul,ol{margin:0 0 1.1em;padding-left:1.2em}
li{margin:0 0 .35em}
a{color:var(--lake);text-underline-offset:3px}
strong{font-weight:700}
:focus-visible{
  outline:2px solid var(--lake);
  outline-offset:2px;
  border-radius:4px;
}

/* ---------- 通用工具 ---------- */
.wrap{
  width:100%;
  max-width:var(--shell);
  margin-inline:auto;
  padding-inline:var(--gutter);
}
.mono{
  font-family:var(--font-mono);
  font-size:.84em;
  letter-spacing:.04em;
}
.eyebrow{
  margin:0 0 .7em;
  font-family:var(--font-mono);
  font-size:12px;
  letter-spacing:.14em;
  text-transform:uppercase;
  color:var(--lake);
}
.lede{
  font-size:20px;
  font-weight:500;
  line-height:1.7;
  color:var(--ink-soft);
}
.rule{
  height:1px;
  margin:0;
  border:0;
  background:var(--line);
}
.section{padding:56px 0}
.section__head{margin-bottom:28px}
.section__title{
  margin:0 0 .35em;
  font-family:var(--font-display);
  font-weight:800;
  font-size:clamp(22px,3vw,34px);
  line-height:1.3;
  color:var(--lake-deep);
}
.dot{
  display:inline-block;
  width:7px;height:7px;
  border-radius:50%;
  background:currentColor;
}
.dot--gold{
  background:var(--gold);
  box-shadow:0 0 0 3px rgba(217,166,60,.22);
}

/* ---------- 网格 ---------- */
.grid-12{
  display:grid;
  grid-template-columns:repeat(12,1fr);
  gap:24px;
}
.col-3{grid-column:span 3}
.col-4{grid-column:span 4}
.col-5{grid-column:span 5}
.col-6{grid-column:span 6}
.col-7{grid-column:span 7}
.col-8{grid-column:span 8}
.col-9{grid-column:span 9}
@media (max-width:899px){
  .col-3,.col-4,.col-5,.col-6,.col-7,.col-8,.col-9{grid-column:1 / -1}
}

/* ---------- 正文容器 ---------- */
.prose{
  max-width:68ch;
  font-size:17px;
  line-height:1.78;
  color:var(--ink);
}
.prose h2{margin:1.6em 0 .5em;font-size:clamp(20px,2.4vw,26px)}
.prose h3{margin:1.4em 0 .4em}
.prose ul,.prose ol{padding-left:1.1em}
.prose blockquote{
  margin:1.4em 0;
  padding:2px 0 2px 18px;
  border-left:2px solid var(--lake);
  color:var(--ink-soft);
}
.prose code{
  font-family:var(--font-mono);
  font-size:.88em;
  background:var(--lake-tint);
  padding:1px 5px;
  border-radius:var(--radius-s);
}

/* ---------- 面包屑 ---------- */
.crumbs{
  display:flex;
  flex-wrap:wrap;
  gap:8px;
  margin:0 0 22px;
  padding:0;
  list-style:none;
  font-family:var(--font-mono);
  font-size:12px;
  color:var(--mist);
}
.crumbs__item{margin:0}
.crumbs__item a{color:var(--lake);text-decoration:none}
.crumbs__item a:hover{text-decoration:underline}
.crumbs__sep{color:rgba(15,63,99,.32)}

/* ---------- 按钮 ---------- */
.btn{
  display:inline-flex;
  align-items:center;
  gap:8px;
  padding:11px 20px;
  border:1px solid transparent;
  border-radius:999px;
  font-size:15px;
  font-weight:600;
  line-height:1.2;
  text-decoration:none;
  cursor:pointer;
  transition:background var(--t-fast) var(--ease),
             color var(--t-fast) var(--ease),
             border-color var(--t-fast) var(--ease),
             transform var(--t-fast) var(--ease);
}
.btn:hover{transform:translateY(-1px)}
.btn:active{transform:translateY(0)}
.btn--solid{background:var(--lake-deep);color:#fff}
.btn--solid:hover{background:var(--lake);color:#fff}
.btn--ghost{background:transparent;color:var(--lake-deep);border-color:var(--lake-deep)}
.btn--ghost:hover{background:var(--lake-soft)}
.btn--quiet{background:var(--lake-soft);color:var(--lake-deep)}
.btn--quiet:hover{background:#CFE4F4}

/* ---------- 标签 ---------- */
.tag{
  display:inline-flex;
  align-items:center;
  gap:6px;
  padding:3px 9px;
  border:1px solid transparent;
  border-radius:999px;
  background:var(--lake-soft);
  color:var(--lake-deep);
  font-family:var(--font-mono);
  font-size:11.5px;
  letter-spacing:.04em;
  line-height:1.6;
}
.tag--grass{background:var(--grass-soft);color:var(--grass)}
.tag--gold{background:rgba(217,166,60,.16);color:#8C6512}
.tag--red{background:rgba(192,82,63,.13);color:var(--red)}
.tag--amber{background:rgba(200,106,34,.13);color:var(--amber)}

/* ---------- 图片容器（页面阶段放置占位图形） ---------- */
.media{margin:0 0 22px}
.media__frame{
  position:relative;
  overflow:hidden;
  border-radius:var(--radius-m);
  background:linear-gradient(120deg,var(--lake-soft),var(--grass-soft));
  border:1px solid var(--line-soft);
}
.media__frame > img,
.media__frame > svg{
  display:block;
  width:100%;
  height:100%;
  object-fit:cover;
}
.media--wide .media__frame{aspect-ratio:16 / 9}
.media--tall .media__frame{aspect-ratio:3 / 4}
.media--band .media__frame{aspect-ratio:21 / 9}
.media__caption{
  margin-top:10px;
  font-family:var(--font-mono);
  font-size:12px;
  letter-spacing:.03em;
  color:var(--mist);
}

/* ---------- 筛选带（仅筛当前页已有内容） ---------- */
.filterbar{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  gap:8px;
  padding:12px 0;
  border-block:1px solid var(--line-soft);
}
.filterbar::before{
  content:"筛选";
  margin-right:6px;
  font-family:var(--font-mono);
  font-size:11.5px;
  letter-spacing:.14em;
  color:var(--mist);
}
.filter-btn{
  padding:7px 14px;
  border:1px solid var(--line);
  border-radius:999px;
  background:transparent;
  color:var(--lake-deep);
  font-size:14px;
  font-weight:500;
  cursor:pointer;
  transition:background var(--t-fast) var(--ease),
             color var(--t-fast) var(--ease),
             border-color var(--t-fast) var(--ease);
}
.filter-btn:hover{background:var(--lake-tint);border-color:var(--lake)}
.filter-btn[aria-pressed="true"]{
  background:var(--lake-deep);
  border-color:var(--lake-deep);
  color:#fff;
  font-weight:600;
}

/* ---------- 侧向锚点索引 ---------- */
.anchor-rail{
  display:flex;
  flex-direction:column;
  gap:2px;
}
.anchor-rail__link{
  padding:6px 10px;
  border-left:2px solid var(--line-soft);
  font-family:var(--font-mono);
  font-size:12px;
  line-height:1.5;
  color:var(--mist);
  text-decoration:none;
  transition:color var(--t-fast) var(--ease),
             background var(--t-fast) var(--ease),
             border-color var(--t-fast) var(--ease);
}
.anchor-rail__link:hover{color:var(--lake-deep);background:var(--lake-tint)}
.anchor-rail__link.is-active{
  color:var(--lake-deep);
  border-left-color:var(--lake);
  background:var(--lake-tint);
  font-weight:500;
}

/* ---------- 显现 ---------- */
[data-reveal]{
  opacity:0;
  transform:translateY(8px);
  transition:opacity var(--t-mid) var(--ease),transform var(--t-mid) var(--ease);
}
[data-reveal].is-visible{opacity:1;transform:none}

/* =========================================================
   页头
   ========================================================= */
.skip-link{
  position:absolute;
  top:-100px;
  left:12px;
  z-index:200;
  padding:10px 16px;
  border-radius:0 0 var(--radius-s) var(--radius-s);
  background:var(--lake-deep);
  color:#fff;
  font-size:14px;
  text-decoration:none;
}
.skip-link:focus{top:0;color:#fff}

.site-header{position:relative;z-index:60}

/* 上层：品牌说明条（低对比） */
.brandbar{
  background:linear-gradient(100deg,var(--lake-soft) 0%,#EDF6FB 55%,#E9F1E9 100%);
  border-bottom:1px solid var(--line-soft);
  color:var(--lake-deep);
}
.brandbar__inner{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  justify-content:space-between;
  gap:10px 24px;
  padding-block:9px;
}
.brandbar__claim{
  display:flex;
  flex-wrap:wrap;
  align-items:baseline;
  gap:10px;
  margin:0;
}
.brandbar__mark{
  font-family:var(--font-display);
  font-size:14px;
  font-weight:800;
  letter-spacing:.04em;
  color:var(--lake-deep);
}
.brandbar__text{
  font-size:13.5px;
  color:#4C5F6D;
}
.brandbar__meta{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  gap:9px 18px;
}
.brandbar__update{
  display:flex;
  align-items:center;
  gap:7px;
  margin:0;
  font-family:var(--font-mono);
  font-size:12px;
  letter-spacing:.03em;
  color:#4C6B80;
}
.utility-link{
  font-size:13px;
  color:var(--lake);
  text-decoration:none;
  border-bottom:1px solid rgba(31,121,183,.35);
  transition:color var(--t-fast) var(--ease),border-color var(--t-fast) var(--ease);
}
.utility-link:hover{color:var(--lake-deep);border-bottom-color:var(--lake-deep)}

/* 下层：主要栏目（高对比） */
.navbar{
  position:sticky;
  top:0;
  background:var(--white);
  border-bottom:1px solid var(--line-soft);
}
.navbar__inner{
  display:flex;
  align-items:center;
  gap:14px;
  padding-block:10px;
}
.navbar__brand{
  display:none;
  align-items:center;
  gap:9px;
  color:var(--lake-deep);
  text-decoration:none;
}
.navbar__brand-mark{
  display:grid;
  place-items:center;
  width:28px;height:28px;
  border-radius:9px;
  background:var(--lake-deep);
  color:#fff;
  font-family:var(--font-display);
  font-size:13px;
  font-weight:800;
}
.navbar__brand-name{
  font-family:var(--font-display);
  font-size:16px;
  font-weight:800;
  letter-spacing:.02em;
}
.nav-list{
  display:flex;
  flex-wrap:wrap;
  gap:2px;
  margin:0 0 0 auto;
  padding:0;
  list-style:none;
  counter-reset:nav;
}
.nav-item{margin:0}
.nav-link{
  display:block;
  padding:9px 12px;
  border-radius:var(--radius-s);
  color:var(--lake-deep);
  font-size:15px;
  font-weight:600;
  line-height:1.3;
  text-decoration:none;
  transition:background var(--t-fast) var(--ease),
             color var(--t-fast) var(--ease),
             box-shadow var(--t-fast) var(--ease);
}
.nav-link::before{
  counter-increment:nav;
  content:"0" counter(nav);
  margin-right:7px;
  font-family:var(--font-mono);
  font-size:10.5px;
  font-weight:400;
  color:var(--mist);
  vertical-align:1px;
}
.nav-link:hover{background:var(--lake-tint);color:var(--lake)}
.nav-link[aria-current="page"]{
  background:var(--lake-soft);
  color:var(--lake-deep);
  box-shadow:inset 0 -2px 0 var(--lake-deep);
}
.nav-link[aria-current="page"]::before{color:var(--gold)}
.nav-cta{
  flex:0 0 auto;
  padding:9px 16px;
  border:1px solid var(--lake-deep);
  border-radius:999px;
  color:var(--lake-deep);
  font-size:14px;
  font-weight:600;
  text-decoration:none;
  transition:background var(--t-fast) var(--ease),color var(--t-fast) var(--ease);
}
.nav-cta:hover{background:var(--lake-deep);color:#fff}

.nav-toggle{
  display:none;
  align-items:center;
  gap:9px;
  margin-left:auto;
  padding:8px 14px;
  border:1px solid var(--line);
  border-radius:999px;
  background:transparent;
  color:var(--lake-deep);
  font-size:13px;
  font-weight:600;
  cursor:pointer;
  transition:background var(--t-fast) var(--ease),border-color var(--t-fast) var(--ease);
}
.nav-toggle:hover{background:var(--lake-tint);border-color:var(--lake)}
.nav-toggle__label{font-family:var(--font-mono);letter-spacing:.06em}
.nav-toggle__bars{display:flex;flex-direction:column;gap:4px}
.nav-toggle__bars i{
  display:block;
  width:15px;height:1.5px;
  background:currentColor;
  transition:transform var(--t-fast) var(--ease);
}
.navbar[data-open] .nav-toggle__bars i:first-child{transform:translateY(2.75px) rotate(45deg)}
.navbar[data-open] .nav-toggle__bars i:last-child{transform:translateY(-2.75px) rotate(-45deg)}

.scroll-progress{
  position:absolute;
  left:0;right:0;bottom:-1px;
  height:2px;
  background:linear-gradient(90deg,var(--lake),var(--grass) 70%,var(--gold));
  transform:scaleX(0);
  transform-origin:0 50%;
  transition:transform 120ms linear;
}

/* =========================================================
   页脚
   ========================================================= */
.site-footer{
  margin-top:88px;
  background:var(--lake-soft);
  color:var(--lake-deep);
  border-top:1px solid rgba(15,63,99,.12);
  font-size:14.5px;
}
.footer-status{
  background:var(--lake-deep);
  color:#EAF3FA;
}
.footer-status__inner{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  gap:8px 14px;
  padding-block:13px;
}
.footer-status__tag{
  margin:0;
  font-size:11.5px;
  letter-spacing:.16em;
  color:#F0C877;
}
.footer-status__text{
  margin:0;
  font-size:14px;
  color:rgba(234,243,250,.88);
}
.footer-status__link{
  margin-left:auto;
  padding-bottom:1px;
  color:#fff;
  font-size:14px;
  font-weight:600;
  text-decoration:none;
  border-bottom:1px solid rgba(255,255,255,.45);
  transition:color var(--t-fast) var(--ease),border-color var(--t-fast) var(--ease);
}
.footer-status__link:hover{color:#F0C877;border-bottom-color:#F0C877}

.footer-grid{
  display:grid;
  grid-template-columns:repeat(2,1fr);
  gap:32px 26px;
  padding-block:48px 40px;
}
@media (min-width:720px){
  .footer-grid{grid-template-columns:repeat(3,1fr)}
}
@media (min-width:1040px){
  .footer-grid{grid-template-columns:1.5fr .9fr 1.3fr 1.2fr .9fr}
}
.footer-brand{margin:0}
.footer-brand__name{
  margin:0 0 .3em;
  font-family:var(--font-display);
  font-size:20px;
  font-weight:800;
  letter-spacing:.02em;
  color:var(--lake-deep);
}
.footer-brand__claim{
  margin:0 0 14px;
  font-size:14px;
  color:#40607A;
}
.footer-brand__mail{
  margin:0 0 8px;
  word-break:break-all;
  font-size:14px;
  color:var(--lake-deep);
}
.footer-brand__mail .mono{
  display:block;
  font-size:11.5px;
  letter-spacing:.12em;
  color:var(--mist);
}
.copy-btn{
  padding:6px 12px;
  border:1px solid var(--line);
  border-radius:999px;
  background:transparent;
  color:var(--lake-deep);
  font-size:11.5px;
  letter-spacing:.06em;
  cursor:pointer;
  transition:background var(--t-fast) var(--ease),border-color var(--t-fast) var(--ease);
}
.copy-btn:hover{background:#fff;border-color:var(--lake)}
.footer-brand__hint{
  margin:10px 0 0;
  font-size:11.5px;
  color:var(--mist);
}

.footer-col{margin:0}
.footer-col__title{
  margin:0 0 .85em;
  padding-bottom:8px;
  border-bottom:1px solid rgba(15,63,99,.16);
  font-family:var(--font-mono);
  font-size:11.5px;
  font-weight:500;
  letter-spacing:.16em;
  color:var(--lake);
}
.footer-list{
  margin:0;
  padding:0;
  list-style:none;
  font-size:14px;
  line-height:1.7;
  color:var(--lake-deep);
}
.footer-list li{margin:0 0 .45em}
.footer-list a{
  color:var(--lake-deep);
  text-decoration:none;
  border-bottom:1px solid transparent;
  transition:color var(--t-fast) var(--ease),border-color var(--t-fast) var(--ease);
}
.footer-list a:hover{color:var(--lake);border-bottom-color:rgba(31,121,183,.5)}
.footer-list--notes{color:#40607A;font-size:13.5px}

.footer-bottom{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  justify-content:space-between;
  gap:8px 20px;
  padding-block:16px 34px;
  border-top:1px solid rgba(15,63,99,.14);
}
.footer-legal{
  margin:0;
  font-size:12.5px;
  color:var(--mist);
}
.footer-legal--mono{font-size:12px;letter-spacing:.06em}

.to-top{
  position:fixed;
  right:var(--gutter);
  bottom:22px;
  z-index:70;
  padding:9px 15px;
  border:1px solid var(--lake-deep);
  border-radius:999px;
  background:var(--white);
  color:var(--lake-deep);
  font-size:13px;
  font-weight:600;
  cursor:pointer;
  opacity:0;
  pointer-events:none;
  transition:opacity var(--t-mid) var(--ease),transform var(--t-mid) var(--ease);
}
.to-top[data-visible]{opacity:1;pointer-events:auto}
.to-top:hover{background:var(--lake-deep);color:#fff}

/* =========================================================
   响应式：移动端把双层导航压成抽屉
   ========================================================= */
@media (max-width:899px){
  .brandbar__inner{padding-block:8px}
  .brandbar__text{display:none}
  .navbar__brand{display:flex}
  .nav-toggle{display:inline-flex}
  .nav-cta{display:none}
  .nav-list{
    position:absolute;
    left:0;right:0;top:100%;
    flex-direction:column;
    flex-wrap:nowrap;
    gap:0;
    max-height:0;
    overflow:hidden;
    visibility:hidden;
    background:var(--white);
    border-bottom:1px solid var(--line);
    box-shadow:0 22px 34px -26px rgba(15,63,99,.5);
    transition:max-height var(--t-fold) var(--ease),visibility 0s linear var(--t-fold);
  }
  .navbar[data-open] .nav-list{
    max-height:72vh;
    overflow-y:auto;
    visibility:visible;
    transition:max-height var(--t-fold) var(--ease),visibility 0s;
  }
  .nav-link{
    padding:14px var(--gutter);
    border-radius:0;
    border-bottom:1px solid var(--line-soft);
  }
  .nav-link[aria-current="page"]{
    background:var(--lake-tint);
    box-shadow:inset 3px 0 0 var(--lake-deep);
  }
}

@media (max-width:719px){
  .footer-status__link{margin-left:0;width:100%}
  .site-footer{margin-top:64px}
  .section{padding:42px 0}
}

/* ---------- 动效降级 ---------- */
@media (prefers-reduced-motion: reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{
    transition-duration:0ms !important;
    animation-duration:0ms !important;
    animation-iteration-count:1 !important;
  }
  [data-reveal]{opacity:1;transform:none}
  .btn:hover,.btn:active{transform:none}
}