/* ==========================================================================
   优乐电子 · 中国区 /assets/site.css
   母题：蓝图细网格 + 四季色带 + 编号索引 + 深蓝粘性色带
   ========================================================================== */

/* 1. Reset
   ========================================================================== */
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body,h1,h2,h3,h4,h5,p,ul,ol,li,figure,blockquote,dl,dd,fieldset{margin:0;padding:0}
ul,ol{list-style:none}
a{color:inherit;text-decoration:none}
button{font:inherit;color:inherit;background:none;border:0;cursor:pointer}
img,picture,svg,video{display:block;max-width:100%}
img{height:auto}
[hidden]{display:none!important}

/* 2. Tokens
   ========================================================================== */
:root{
  --blueprint:#0A1B3D;
  --brand:#1E56C8;
  --brand-bright:#4C86F0;
  --mist:#E6EDFB;
  --spring:#0F9E8A;
  --spring-deep:#0B7A6B;
  --summer:#EE5F3B;
  --autumn:#C98A12;
  --winter:#6C5BD4;
  --ink:#101828;
  --grey:#5A6478;
  --paper:#F6F8FC;
  --grid:#D3DBEA;

  --font-display:"Noto Sans SC","Source Han Sans SC","PingFang SC","Microsoft YaHei",system-ui,sans-serif;
  --font-body:"Noto Sans SC","Source Han Sans SC","PingFang SC","Microsoft YaHei",system-ui,sans-serif;
  --font-mono:"IBM Plex Mono","SFMono-Regular",ui-monospace,"Cascadia Mono","Consolas",monospace;

  --max:1280px;
  --gutter:clamp(16px,3.4vw,40px);
  --line:1px solid var(--grid);
  --cell:24px;
  --shadow-head:0 1px 0 rgba(10,27,61,.06);
  --ease:cubic-bezier(.2,.7,.3,1);
}

/* 3. Base
   ========================================================================== */
body{
  background:var(--paper);
  color:var(--ink);
  font-family:var(--font-body);
  font-size:17px;
  line-height:1.75;
  font-weight:400;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
h1,h2,h3,h4,h5{
  font-family:var(--font-display);
  font-weight:900;
  letter-spacing:-.02em;
  line-height:1.15;
  color:var(--ink);
}
h1{font-size:clamp(34px,5.2vw,64px)}
h2{font-size:clamp(26px,3.4vw,40px)}
h3{font-size:clamp(20px,2.2vw,28px)}
h4{font-size:clamp(17px,1.6vw,20px);letter-spacing:-.01em}
p{max-width:720px}
strong{font-weight:700}
::selection{background:var(--brand);color:#fff}
:focus-visible{outline:3px solid var(--brand-bright);outline-offset:3px}
.site-footer :focus-visible{outline-color:#fff}

/* 4. 通用骨架
   ========================================================================== */
.container{
  width:100%;
  max-width:var(--max);
  margin-inline:auto;
  padding-inline:var(--gutter);
}
.container--narrow{max-width:840px}
.section{padding-block:clamp(40px,6vw,80px)}
.section--mist{
  background:var(--mist);
  border-block:var(--line);
  background-image:
    linear-gradient(to right,rgba(211,219,234,.55) 1px,transparent 1px),
    linear-gradient(to bottom,rgba(211,219,234,.55) 1px,transparent 1px);
  background-size:var(--cell) var(--cell);
}
.rule{height:1px;background:var(--grid);border:0;margin:0}
.prose{max-width:720px}
.prose p + p{margin-top:1.4em}
.prose ul{max-width:720px;display:grid;gap:.5em;padding-left:1.1em;list-style:square}
.eyebrow{
  display:inline-flex;align-items:center;gap:8px;
  font-family:var(--font-mono);font-size:12px;font-weight:500;
  letter-spacing:.12em;line-height:1.4;color:var(--brand);
}
.grid{
  display:grid;
  gap:clamp(16px,2.4vw,28px);
  grid-template-columns:repeat(var(--cols,12),minmax(0,1fr));
}
.split{
  display:grid;
  gap:clamp(24px,4vw,48px);
  grid-template-columns:minmax(0,5fr) minmax(0,7fr);
  align-items:start;
}
.breadcrumbs{
  display:flex;flex-wrap:wrap;align-items:center;gap:6px 10px;
  padding-block:16px;
  font-family:var(--font-mono);font-size:11px;letter-spacing:.08em;
  color:var(--grey);
}
.breadcrumbs a{color:var(--brand);border-bottom:1px solid transparent}
.breadcrumbs a:hover{border-bottom-color:currentColor}
.breadcrumbs__sep{color:var(--grid)}
.breadcrumbs [aria-current="page"]{color:var(--ink)}

/* 5. 按钮
   ========================================================================== */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:.5em;
  padding:.78em 1.25em;
  font-family:var(--font-display);font-size:14px;font-weight:700;
  letter-spacing:.04em;line-height:1;text-align:center;
  border:1px solid transparent;border-radius:0;
  transition:background .18s var(--ease),color .18s var(--ease),border-color .18s var(--ease),transform .18s var(--ease);
}
.btn:active{transform:translateY(1px)}
.btn--primary{background:var(--brand);border-color:var(--brand);color:#fff}
.btn--primary:hover{background:var(--blueprint);border-color:var(--blueprint);color:#fff}
.btn--ghost{background:transparent;border-color:var(--brand);color:var(--brand)}
.btn--ghost:hover{background:var(--mist);border-color:var(--blueprint);color:var(--blueprint)}

/* 6. 标签
   ========================================================================== */
.tag{
  display:inline-flex;align-items:center;gap:6px;
  padding:5px 10px;
  font-family:var(--font-display);font-size:12px;font-weight:700;
  letter-spacing:.08em;line-height:1.3;
  border:1px solid transparent;border-radius:0;white-space:nowrap;
}
.tag--spring{background:var(--spring-deep);border-color:var(--spring-deep);color:#fff}
.tag--summer{background:var(--summer);border-color:var(--summer);color:var(--blueprint)}
.tag--autumn{background:var(--autumn);border-color:var(--autumn);color:var(--blueprint)}
.tag--winter{background:var(--winter);border-color:var(--winter);color:#fff}
.tag--outline{background:transparent;border-color:var(--grid);color:var(--grey)}

/* 7. 图片容器基础
   ========================================================================== */
.media{
  position:relative;display:block;overflow:hidden;
  aspect-ratio:16 / 9;
  border:var(--line);
  background:
    linear-gradient(135deg,rgba(30,86,200,.14),rgba(108,91,212,.10) 60%,rgba(15,158,138,.12));
  background-color:var(--mist);
}
.media > img,.media > picture > img{width:100%;height:100%;object-fit:cover}
.media--4x3{aspect-ratio:4 / 3}
.media--1x1{aspect-ratio:1 / 1}
.media--wide{aspect-ratio:21 / 9}
.media__tag{
  position:absolute;top:0;left:0;z-index:2;
  padding:6px 10px;
  font-family:var(--font-mono);font-size:11px;font-weight:500;letter-spacing:.08em;
  background:var(--blueprint);color:#fff;
}
.media__grid{
  position:absolute;inset:0;z-index:1;pointer-events:none;
  background-image:
    linear-gradient(to right,rgba(10,27,61,.10) 1px,transparent 1px),
    linear-gradient(to bottom,rgba(10,27,61,.10) 1px,transparent 1px);
  background-size:var(--cell) var(--cell);
}

/* 8. 跳转链接
   ========================================================================== */
.skip-link{
  position:fixed;top:10px;left:10px;z-index:300;
  padding:10px 16px;
  font-family:var(--font-display);font-size:13px;font-weight:700;letter-spacing:.04em;
  background:var(--blueprint);color:#fff;border:1px solid var(--brand-bright);
  transform:translateY(-180%);
  transition:transform .18s var(--ease);
}
.skip-link:focus,.skip-link:focus-visible{transform:translateY(0)}

/* 9. 页头
   ========================================================================== */
.site-header{
  position:sticky;top:0;z-index:100;
  background:var(--paper);
  border-bottom:var(--line);
  box-shadow:var(--shadow-head);
  transition:background .22s var(--ease),border-color .22s var(--ease),box-shadow .22s var(--ease);
}
/* 顶部四季色带 */
.season-band{
  position:relative;display:flex;
  height:6px;overflow:hidden;
  background:var(--blueprint);
}
.season-band__seg{display:block;height:100%}
.season-band__seg--blueprint{flex:0 0 clamp(48px,7vw,96px);background:var(--blueprint)}
.season-band__seg--spring{flex:0 0 32%;background:var(--spring)}
.season-band__seg--summer{flex:0 0 20%;background:var(--summer)}
.season-band__seg--autumn{flex:0 0 24%;background:var(--autumn)}
.season-band__seg--winter{flex:1 1 auto;background:var(--winter)}
.season-band__ticks{
  position:absolute;inset:0;pointer-events:none;opacity:.5;
  background-image:repeating-linear-gradient(90deg,rgba(10,27,61,.6) 0 1px,transparent 1px 12px);
}
.header-bar{position:relative}
.header-inner{
  width:100%;max-width:var(--max);margin-inline:auto;
  padding:16px var(--gutter);
  display:flex;align-items:center;justify-content:space-between;gap:24px;
  transition:padding .22s var(--ease);
}
/* 品牌 */
.brand{display:flex;align-items:center;gap:12px;min-width:0}
.brand__dot{
  flex:none;width:14px;height:14px;
  background:
    linear-gradient(135deg,var(--spring) 0 25%,var(--summer) 25% 50%,var(--autumn) 50% 75%,var(--winter) 75% 100%);
  box-shadow:0 0 0 4px rgba(30,86,200,.10);
}
.brand__text{display:block;min-width:0}
.brand__name{
  display:block;
  font-family:var(--font-display);font-size:19px;font-weight:900;
  letter-spacing:-.02em;line-height:1.2;color:var(--ink);
}
.brand__region{font-size:12px;font-weight:500;letter-spacing:.06em;color:var(--grey)}
.brand__tagline{
  display:block;margin-top:3px;
  font-family:var(--font-mono);font-size:11px;font-weight:500;
  letter-spacing:.1em;line-height:1.4;color:var(--grey);
  transition:opacity .18s var(--ease),transform .18s var(--ease);
}
/* 右侧导航组 */
.header-right{display:flex;align-items:center;gap:18px;min-width:0}
.primary-nav{min-width:0}
.primary-nav__list{display:flex;align-items:center;gap:2px}
.primary-nav__link{
  position:relative;
  display:inline-flex;align-items:baseline;gap:6px;
  padding:10px 12px;
  font-family:var(--font-display);font-size:15px;font-weight:500;line-height:1.4;
  color:var(--ink);
  transition:color .18s var(--ease);
}
.primary-nav__idx{
  font-family:var(--font-mono);font-size:10px;font-weight:500;
  letter-spacing:.08em;color:var(--grey);
  transition:color .18s var(--ease);
}
.primary-nav__link::after{
  content:"";position:absolute;left:12px;right:12px;bottom:2px;height:2px;
  background:var(--brand);
  transform:scaleX(0);transform-origin:left center;
  transition:transform .18s var(--ease);
}
.primary-nav__link:hover{color:var(--brand)}
.primary-nav__link:hover::after{transform:scaleX(1)}
.primary-nav__link[aria-current="page"]{color:var(--brand);font-weight:700}
.primary-nav__link[aria-current="page"]::after{transform:scaleX(1)}
.primary-nav__link[aria-current="page"] .primary-nav__idx{color:var(--brand)}
.header-cta{flex:none;white-space:nowrap}
/* 移动按钮 */
.nav-toggle{
  display:none;align-items:center;gap:8px;
  padding:10px 12px;
  border:1px solid var(--grid);background:var(--mist);
  font-family:var(--font-display);font-size:12px;font-weight:700;letter-spacing:.1em;
  color:var(--blueprint);
  transition:background .18s var(--ease),border-color .18s var(--ease),color .18s var(--ease);
}
.nav-toggle:hover{background:#fff;border-color:var(--brand)}
.nav-toggle__bars{position:relative;display:block;width:16px;height:10px;flex:none}
.nav-toggle__bars span{
  position:absolute;left:0;right:0;height:2px;background:currentColor;
  transition:transform .2s var(--ease),opacity .2s var(--ease);
}
.nav-toggle__bars span:first-child{top:0}
.nav-toggle__bars span:last-child{bottom:0}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars span:first-child{transform:translateY(4px) rotate(45deg)}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars span:last-child{transform:translateY(-4px) rotate(-45deg)}
.nav-toggle__label{display:block;line-height:1}
/* 阅读进度 */
.read-progress{
  position:absolute;left:0;right:0;bottom:-1px;height:2px;
  background:rgba(30,86,200,.12);
}
.read-progress__bar{
  display:block;height:100%;width:0;
  background:linear-gradient(90deg,var(--brand),var(--brand-bright));
  transition:width .1s linear;
}
/* 压缩态：滚动后成一条 56px 深蓝色带 */
.site-header[data-condensed="true"]{
  background:var(--blueprint);
  border-bottom-color:rgba(211,219,234,.22);
  box-shadow:0 6px 24px rgba(10,27,61,.28);
}
.site-header[data-condensed="true"] .header-inner{padding-block:9px}
.site-header[data-condensed="true"] .brand__name{color:#fff}
.site-header[data-condensed="true"] .brand__region{color:rgba(230,237,251,.72)}
.site-header[data-condensed="true"] .brand__tagline{display:none}
.site-header[data-condensed="true"] .primary-nav__link{color:#DCE6FB;font-size:14px;padding-block:8px}
.site-header[data-condensed="true"] .primary-nav__idx{color:var(--brand-bright)}
.site-header[data-condensed="true"] .primary-nav__link:hover{color:#fff}
.site-header[data-condensed="true"] .primary-nav__link::after{background:var(--brand-bright)}
.site-header[data-condensed="true"] .primary-nav__link[aria-current="page"]{color:#fff}
.site-header[data-condensed="true"] .primary-nav__link[aria-current="page"] .primary-nav__idx{color:var(--brand-bright)}
.site-header[data-condensed="true"] .nav-toggle{
  background:rgba(255,255,255,.08);border-color:rgba(230,237,251,.35);color:#fff;
}
.site-header[data-condensed="true"] .btn--primary{
  background:var(--brand-bright);border-color:var(--brand-bright);color:var(--blueprint);
}
.site-header[data-condensed="true"] .btn--primary:hover{background:#fff;border-color:#fff;color:var(--blueprint)}
.site-header[data-condensed="true"] .read-progress{background:rgba(255,255,255,.14)}

/* 10. 页脚
   ========================================================================== */
.site-footer{
  position:relative;overflow:hidden;
  padding-block:clamp(40px,5vw,64px) 28px;
  background:var(--blueprint);
  color:var(--mist);
}
.site-footer::before{
  content:"";position:absolute;inset:0;pointer-events:none;
  background-image:
    linear-gradient(to right,rgba(211,219,234,.09) 1px,transparent 1px),
    linear-gradient(to bottom,rgba(211,219,234,.09) 1px,transparent 1px);
  background-size:var(--cell) var(--cell);
}
.footer-inner{
  position:relative;z-index:1;
  width:100%;max-width:var(--max);margin-inline:auto;
  padding-inline:var(--gutter);
}
.footer-top{
  display:flex;flex-wrap:wrap;align-items:flex-end;justify-content:space-between;
  gap:24px;
  padding-bottom:26px;
  border-bottom:1px solid rgba(211,219,234,.22);
}
.footer-brand__name{
  font-family:var(--font-display);font-weight:900;
  font-size:clamp(20px,2.6vw,26px);letter-spacing:-.02em;line-height:1.2;
  color:#fff;max-width:none;
}
.footer-brand__meta{
  margin-top:8px;max-width:none;
  font-family:var(--font-mono);font-size:11px;font-weight:500;
  letter-spacing:.12em;color:rgba(230,237,251,.62);
}
.footer-seasons{display:flex;align-items:center;gap:6px;flex-wrap:wrap}
.footer-seasons__chip{display:block;height:6px}
.footer-seasons__chip--spring{width:52px;background:var(--spring)}
.footer-seasons__chip--summer{width:32px;background:var(--summer)}
.footer-seasons__chip--autumn{width:42px;background:var(--autumn)}
.footer-seasons__chip--winter{width:24px;background:var(--winter)}
.footer-grid{
  display:grid;
  grid-template-columns:repeat(4,minmax(0,1fr));
  gap:clamp(24px,3vw,40px);
  padding-block:32px;
}
.footer-col{min-width:0}
.footer-col__title{
  display:flex;align-items:baseline;gap:8px;
  padding-bottom:10px;margin-bottom:14px;
  border-bottom:1px solid rgba(211,219,234,.22);
  font-family:var(--font-display);font-size:13px;font-weight:700;
  letter-spacing:.14em;line-height:1.4;color:#fff;
}
.footer-col__num{
  font-family:var(--font-mono);font-size:11px;font-weight:500;
  letter-spacing:.08em;color:var(--brand-bright);
}
.footer-col__list{
  display:grid;gap:9px;
  font-size:14px;line-height:1.65;color:rgba(230,237,251,.82);
}
.footer-link{
  color:rgba(230,237,251,.88);
  border-bottom:1px solid transparent;
  transition:color .18s var(--ease),border-color .18s var(--ease);
}
.footer-link:hover{color:#fff;border-bottom-color:var(--brand-bright)}
.footer-contact{
  font-family:var(--font-mono);font-size:13px;font-weight:500;
  letter-spacing:.02em;color:#fff;
  overflow-wrap:anywhere;
}
.footer-legal{
  display:flex;flex-wrap:wrap;justify-content:space-between;gap:8px 24px;
  padding-top:22px;
  border-top:1px solid rgba(211,219,234,.22);
  font-size:12px;line-height:1.7;color:rgba(230,237,251,.66);
}
.footer-legal__line,.footer-legal__meta{max-width:none}
.footer-legal__meta{
  font-family:var(--font-mono);letter-spacing:.08em;
  color:rgba(230,237,251,.52);
}

/* 11. 侧边索引 / 章节高亮
   ========================================================================== */
.spy-link{
  position:relative;display:flex;align-items:baseline;gap:8px;
  padding:8px 0 8px 14px;
  border-left:1px solid var(--grid);
  font-size:14px;line-height:1.5;color:var(--grey);
  transition:color .18s var(--ease),border-color .18s var(--ease),background .18s var(--ease);
}
.spy-link:hover{color:var(--brand);border-left-color:var(--brand-bright)}
.spy-link[aria-current="true"]{
  color:var(--blueprint);font-weight:700;
  border-left-color:var(--brand);
  box-shadow:inset 2px 0 0 var(--brand);
  background:linear-gradient(90deg,rgba(30,86,200,.08),transparent);
}

/* 12. 动效
   ========================================================================== */
.js [data-reveal]{
  opacity:0;transform:translateY(14px);
  transition:opacity .5s var(--ease),transform .5s var(--ease);
}
.js [data-reveal].is-visible{opacity:1;transform:none}

/* 13. 响应式
   ========================================================================== */
@media (max-width:1080px){
  .primary-nav__link{font-size:14px;padding-inline:9px}
  .primary-nav__link::after{left:9px;right:9px}
  .header-right{gap:12px}
}

@media (max-width:960px){
  .nav-toggle{display:inline-flex}
  .header-right{gap:10px}
  .primary-nav{
    position:absolute;top:100%;left:0;right:0;z-index:120;
    max-height:calc(100vh - 72px);overflow-y:auto;
    background:var(--blueprint);
    background-image:
      linear-gradient(to right,rgba(211,219,234,.10) 1px,transparent 1px),
      linear-gradient(to bottom,rgba(211,219,234,.10) 1px,transparent 1px);
    background-size:var(--cell) var(--cell);
    border-block:1px solid rgba(211,219,234,.24);
    visibility:hidden;opacity:0;pointer-events:none;
    transform:translateY(-10px);
    transition:opacity .2s var(--ease),transform .2s var(--ease),visibility .2s var(--ease);
  }
  .primary-nav[data-open]{
    visibility:visible;opacity:1;pointer-events:auto;transform:none;
  }
  .primary-nav__list{flex-direction:column;align-items:stretch;gap:0}
  .primary-nav__link{
    flex-direction:row-reverse;justify-content:space-between;
    width:100%;padding:15px var(--gutter);
    font-size:16px;color:#E6EDFB;
    border-bottom:1px solid rgba(211,219,234,.14);
  }
  .primary-nav__link::after{display:none}
  .primary-nav__idx{color:var(--brand-bright);font-size:11px}
  .primary-nav__link[aria-current="page"]{
    color:#fff;background:rgba(76,134,240,.18);
    box-shadow:inset 3px 0 0 var(--brand-bright);
  }
  .site-header[data-condensed="true"] .primary-nav__link{padding-block:15px}
  .split{grid-template-columns:minmax(0,1fr)}
}

@media (max-width:860px){
  body{font-size:16px}
  .footer-grid{grid-template-columns:repeat(2,minmax(0,1fr))}
}

@media (max-width:720px){
  .header-cta{display:none}
  .grid{grid-template-columns:minmax(0,1fr)}
}

@media (max-width:560px){
  .brand__tagline{display:none}
  .brand__name{font-size:17px}
  .footer-grid{grid-template-columns:minmax(0,1fr);gap:24px}
  .footer-legal{flex-direction:column;align-items:flex-start}
  .media{aspect-ratio:4 / 3}
  .media--wide{aspect-ratio:16 / 9}
}

/* 14. 降低动效
   ========================================================================== */
@media (prefers-reduced-motion: reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{
    animation-duration:.001ms!important;
    animation-iteration-count:1!important;
    transition-duration:.001ms!important;
    scroll-behavior:auto!important;
  }
  .js [data-reveal]{opacity:1;transform:none}
  .skip-link{transition:none}
}