/* ============================================================
   YaoNav — a light, flat index for electronics engineers
   ============================================================ */
:root{
  --header-h:64px;
  --bg:#f6f8fc;
  --surface:#fff;
  --surface-2:#f0f4fa;
  --surface-hover:#fbfcff;
  --ink:#0a1222;
  --ink-2:#354158;
  --muted:#66748b;
  --faint:#8a96aa;
  --line:#e3e9f3;
  --line-strong:#cfd9e8;
  --blue:#2563eb;
  --blue-solid:#2563eb;
  --blue-soft:#eaf1ff;
  --blue-ring:rgba(37,99,235,.15);
  --header:rgba(246,248,252,.82);
  --grid:rgba(37,99,235,.055);
  --hero-wash:rgba(37,99,235,.10);
  --sans:"Inter","HarmonyOS Sans SC","MiSans","PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,-apple-system,"Segoe UI",sans-serif;
  --mono:"SFMono-Regular","Cascadia Code","JetBrains Mono",ui-monospace,Consolas,monospace;
}
[data-theme="dark"]{
  --bg:#070b14;
  --surface:#0d1422;
  --surface-2:#111a2b;
  --surface-hover:#101a2c;
  --ink:#e9eff9;
  --ink-2:#b4c0d4;
  --muted:#8491a8;
  --faint:#637088;
  --line:#1b2740;
  --line-strong:#2a3b57;
  --blue:#7aa2ff;
  --blue-solid:#2f62d8;
  --blue-soft:#12213c;
  --blue-ring:rgba(91,141,255,.22);
  --header:rgba(7,11,20,.82);
  --grid:rgba(91,141,255,.06);
  --hero-wash:rgba(37,99,235,.18);
}
*,*::before,*::after{box-sizing:border-box}
html{
  background:var(--bg);
  scroll-behavior:smooth;
  scroll-padding-top:var(--header-h);
  -webkit-text-size-adjust:100%;
}
body{
  margin:0;
  background:var(--bg);
  color:var(--ink);
  font-family:var(--sans);
  font-size:15px;
  line-height:1.6;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
  overflow-x:clip;
}
::selection{background:var(--blue-solid);color:#fff}
a{color:inherit;text-decoration:none}
button,input{font:inherit}
button{color:inherit}
img,svg{display:block}
h1,h2,h3,p{margin:0}
[hidden]{display:none!important}
.shell{
  width:100%;
  max-width:1200px;
  margin:0 auto;
  padding-inline:clamp(18px,4vw,32px);
}
.sr-only{
  position:absolute;width:1px;height:1px;padding:0;margin:-1px;
  overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0;
}
.skip{
  position:fixed;left:14px;top:-60px;z-index:100;
  padding:9px 14px;border-radius:8px;background:var(--surface);
  border:1px solid var(--line-strong);color:var(--ink);font-size:13px;
  transition:top .18s ease;
}
.skip:focus{top:12px}
:focus-visible{outline:2px solid var(--blue);outline-offset:2px}

/* ---------------- top bar ---------------- */
.topbar{
  position:sticky;top:0;z-index:60;
  height:var(--header-h);
  background:var(--header);
  border-bottom:1px solid transparent;
  backdrop-filter:blur(18px) saturate(1.35);
  -webkit-backdrop-filter:blur(18px) saturate(1.35);
  transition:border-color .2s ease,background .2s ease;
}
.topbar.is-stuck{border-bottom-color:var(--line)}
.topbar-inner{height:100%;display:flex;align-items:center;gap:22px}
.brand{display:inline-flex;align-items:center;gap:9px;flex:0 0 auto;border-radius:8px}
.brand img{width:30px;height:30px}
.brand-name{
  display:flex;align-items:baseline;gap:7px;
  font-size:15px;font-weight:670;letter-spacing:-.025em;line-height:1;
  transition:color .18s ease;
}
.brand:hover .brand-name{color:var(--blue)}
.brand-cn{
  font-size:12px;font-weight:450;letter-spacing:0;
  color:var(--muted);
}
.topnav{display:flex;align-items:center;gap:22px;margin-left:auto}
.topnav a{
  position:relative;padding:5px 0;font-size:13px;color:var(--ink-2);
  transition:color .18s ease;
}
.topnav a::after{
  content:"";position:absolute;left:0;right:100%;bottom:0;height:1px;
  background:var(--blue);transition:right .22s ease;
}
.topnav a:hover{color:var(--ink)}
.topnav a:hover::after{right:0}
.top-actions{display:flex;align-items:center;gap:7px}
.icon-btn{
  width:34px;height:34px;display:grid;place-items:center;
  padding:0;border:1px solid transparent;border-radius:8px;
  background:transparent;color:var(--ink-2);cursor:pointer;
  transition:background .18s ease,border-color .18s ease,color .18s ease;
}
.icon-btn:hover{background:var(--surface);border-color:var(--line);color:var(--ink)}
.theme-switch{
  display:flex;align-items:center;gap:1px;height:34px;padding:3px;
  border:1px solid var(--line);border-radius:9px;background:var(--surface);
}
.theme-switch button{
  width:28px;height:26px;display:grid;place-items:center;padding:0;
  border:0;border-radius:6px;background:transparent;color:var(--muted);
  cursor:pointer;transition:background .18s ease,color .18s ease;
}
.theme-switch button:hover{background:var(--surface-2);color:var(--ink)}
.theme-switch button[aria-pressed="true"]{background:var(--blue-soft);color:var(--blue)}

/* ---------------- hero ---------------- */
.hero{
  position:relative;
  overflow:clip;
  padding:clamp(64px,8.6vw,108px) 0 clamp(40px,5.5vw,62px);
  background:radial-gradient(740px 440px at 50% -18%,var(--hero-wash),transparent 72%);
}
.hero::before{
  content:"";position:absolute;inset:0;z-index:0;pointer-events:none;
  background-image:
    linear-gradient(var(--grid) 1px,transparent 1px),
    linear-gradient(90deg,var(--grid) 1px,transparent 1px);
  background-size:54px 54px;
  mask-image:radial-gradient(ellipse 62% 64% at 50% 32%,#000 0%,transparent 74%);
  -webkit-mask-image:radial-gradient(ellipse 62% 64% at 50% 32%,#000 0%,transparent 74%);
  opacity:.7;
}
.hero-inner{position:relative;z-index:1;text-align:center}
.eyebrow{
  display:inline-flex;align-items:center;gap:9px;
  font-family:var(--mono);font-size:10.5px;letter-spacing:.11em;
  color:var(--blue);text-transform:uppercase;
}
.eyebrow .dot{
  width:5px;height:5px;border-radius:50%;background:var(--blue);
  box-shadow:0 0 0 4px var(--blue-soft);
}
.eyebrow-slash{color:var(--line-strong);margin:0 1px}
.hero h1{
  margin-top:20px;
  font-size:clamp(42px,6.6vw,72px);
  line-height:1.06;
  letter-spacing:-.06em;
  font-weight:720;
  color:var(--ink);
}
.hero h1 span{color:var(--blue)}
.lead{
  max-width:590px;margin:22px auto 0;
  font-size:15.5px;line-height:1.85;color:var(--ink-2);
}
.lead b{font-weight:650;color:var(--ink);font-variant-numeric:tabular-nums}
.search{
  position:relative;display:flex;align-items:center;gap:11px;
  width:min(100%,690px);height:58px;margin:34px auto 0;
  padding:0 13px 0 17px;
  border:1px solid var(--line-strong);border-radius:16px;
  background:var(--surface);
  text-align:left;
  transition:border-color .2s ease,box-shadow .2s ease;
}
.search:focus-within{
  border-color:var(--blue);
  box-shadow:0 0 0 4px var(--blue-ring);
}
.search-ico{flex:0 0 auto;color:var(--muted)}
.search input{
  flex:1;min-width:0;height:100%;padding:0;
  border:0;outline:0;background:transparent;color:var(--ink);
  font-size:14.5px;letter-spacing:-.005em;
}
.search input::placeholder{color:var(--faint)}
.search input::-webkit-search-cancel-button{display:none}
.keyhint{
  flex:0 0 auto;font-family:var(--mono);font-size:10.5px;
  color:var(--muted);background:var(--surface-2);
  border:1px solid var(--line);border-radius:5px;
  padding:2px 7px;line-height:1.45;
}
.search-clear{
  flex:0 0 auto;width:24px;height:24px;display:grid;place-items:center;
  padding:0;border:0;border-radius:5px;background:var(--surface-2);
  color:var(--muted);cursor:pointer;
}
.search-clear:hover{background:var(--line);color:var(--ink)}
.hot{
  display:flex;align-items:center;justify-content:center;flex-wrap:wrap;gap:3px;
  margin-top:13px;font-size:12px;color:var(--faint);
}
.hot>span{margin-right:3px}
.hot button{
  padding:3px 7px;border:0;border-radius:5px;background:transparent;
  color:var(--ink-2);font-size:12px;cursor:pointer;
  transition:background .16s ease,color .16s ease;
}
.hot button:hover{background:var(--blue-soft);color:var(--blue)}
.hero-meta{
  display:flex;align-items:center;justify-content:center;flex-wrap:wrap;gap:12px;
  margin-top:26px;color:var(--muted);font-size:12px;
}
.hero-meta b{font-weight:650;color:var(--ink-2);font-variant-numeric:tabular-nums}
.hero-meta i{width:3px;height:3px;border-radius:50%;background:var(--line-strong)}

/* ---------------- filter dock ---------------- */
.filter-dock{
  position:sticky;top:var(--header-h);z-index:45;
  background:var(--header);
  border-bottom:1px solid var(--line);
  backdrop-filter:blur(18px) saturate(1.3);
  -webkit-backdrop-filter:blur(18px) saturate(1.3);
}
.filter-row{position:relative}
.filters{
  display:flex;align-items:center;gap:8px;
  padding:12px 0;
  overflow-x:auto;
  scrollbar-width:none;
  -webkit-overflow-scrolling:touch;
}
.filters::-webkit-scrollbar{display:none}
.chip{
  display:inline-flex;align-items:center;height:38px;padding:0 14px;
  border:1px solid var(--line);border-radius:9px;
  background:var(--surface);color:var(--ink-2);
  font-size:13.5px;font-weight:500;line-height:1;white-space:nowrap;cursor:pointer;
  transition:border-color .18s ease,background .18s ease,color .18s ease,opacity .18s ease;
}
.chip:hover{border-color:var(--line-strong);color:var(--ink)}
.chip .n{
  margin-left:5px;font-family:var(--mono);font-size:10.5px;
  color:var(--faint);font-weight:400;
}
.chip[aria-pressed="true"]{
  border-color:var(--blue-solid);
  background:var(--blue-solid);
  color:#fff;
}
.chip[aria-pressed="true"] .n{color:rgba(255,255,255,.7)}
.chip.is-empty:not([aria-pressed="true"]){opacity:.55}

/* ---------------- directory ---------------- */
.directory{padding-top:clamp(30px,4vw,46px)}
.dir-head{
  display:flex;align-items:flex-end;justify-content:space-between;gap:24px;
  margin-bottom:18px;
}
.kicker{
  margin-bottom:8px;
  font-family:var(--mono);font-size:10px;letter-spacing:.15em;
  color:var(--blue);
}
.dir-head h2{
  font-size:clamp(23px,2.6vw,29px);
  line-height:1.2;letter-spacing:-.04em;font-weight:680;
}
.view-desc{margin-top:6px;color:var(--muted);font-size:12.5px}
.result-count{
  flex:0 0 auto;padding-bottom:3px;
  color:var(--muted);font-size:12px;font-variant-numeric:tabular-nums;
}
.grid{
  display:grid;
  grid-template-columns:repeat(4,minmax(0,1fr));
  gap:16px;
  margin-top:26px;
}
.site{
  --cat:#2563eb;--cat-bg:#edf3ff;
  position:relative;display:flex;align-items:flex-start;gap:14px;
  min-height:100px;padding:18px 17px;
  border:1px solid var(--line);border-radius:15px;
  background:var(--surface);
  transition:border-color .18s ease,background .18s ease,transform .18s ease;
}
.site:hover{
  transform:translateY(-2px);
  border-color:color-mix(in srgb,var(--cat) 38%,var(--line));
  background:var(--surface-hover);
}
.site:active{transform:translateY(0)}
.site-mark{
  flex:0 0 46px;width:46px;height:46px;
  display:grid;place-items:center;
  border:1px solid color-mix(in srgb,var(--cat) 13%,var(--cat-bg));
  border-radius:12px;
  background:var(--cat-bg);color:var(--cat);
  font-family:var(--mono);font-size:12px;font-weight:700;line-height:1;
  letter-spacing:-.04em;text-align:center;
  transition:border-color .18s ease;
}
.site:hover .site-mark{border-color:color-mix(in srgb,var(--cat) 28%,var(--cat-bg))}
.site-copy{min-width:0;flex:1;padding-top:2px}
.site-name-row{display:flex;align-items:center;gap:5px;min-width:0}
.site-name{
  min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;
  font-size:14.5px;font-weight:630;letter-spacing:-.015em;line-height:1.45;
}
.site-arrow{
  flex:0 0 auto;margin-left:auto;transform:translate(-2px,2px);
  color:var(--faint);font-family:var(--mono);font-size:13px;line-height:1;
  opacity:.55;transition:opacity .18s ease,transform .18s ease,color .18s ease;
}
.site:hover .site-arrow{opacity:1;color:var(--cat);transform:translate(0,0)}
.site-desc{
  display:-webkit-box;margin-top:5px;overflow:hidden;
  -webkit-box-orient:vertical;-webkit-line-clamp:2;
  color:var(--muted);font-size:12px;line-height:1.6;
}
.cat-academic{--cat:#1d4ed8;--cat-bg:#edf3ff}
.cat-datasheet{--cat:#0e7490;--cat-bg:#ecfeff}
.cat-chips{--cat:#4f46e5;--cat-bg:#eef0ff}
.cat-eda{--cat:#7e22ce;--cat-bg:#f6f0ff}
.cat-foundry{--cat:#b45309;--cat-bg:#fff7e8}
.cat-news{--cat:#be123c;--cat-bg:#fff1f4}
.cat-community{--cat:#0f766e;--cat-bg:#ecfdf8}
.cat-learn{--cat:#15803d;--cat-bg:#f0fdf4}
.cat-cloud{--cat:#475569;--cat-bg:#f1f5f9}
[data-theme="dark"] .cat-academic{--cat:#8ab0ff;--cat-bg:#132343}
[data-theme="dark"] .cat-datasheet{--cat:#67e8f9;--cat-bg:#0b2a33}
[data-theme="dark"] .cat-chips{--cat:#b4b8ff;--cat-bg:#1a1b42}
[data-theme="dark"] .cat-eda{--cat:#d0b5ff;--cat-bg:#26163f}
[data-theme="dark"] .cat-foundry{--cat:#fbbf24;--cat-bg:#33240e}
[data-theme="dark"] .cat-news{--cat:#fda4b4;--cat-bg:#35121d}
[data-theme="dark"] .cat-community{--cat:#5eead4;--cat-bg:#0c2f2c}
[data-theme="dark"] .cat-learn{--cat:#86efac;--cat-bg:#0e2c18}
[data-theme="dark"] .cat-cloud{--cat:#cbd5e1;--cat-bg:#1a2434}

/* ---------------- empty + loading ---------------- */
.empty{
  padding:64px 22px;
  border:1px dashed var(--line-strong);border-radius:16px;
  text-align:center;color:var(--muted);
}
.empty svg{margin:0 auto;color:var(--faint)}
.empty h3{margin-top:14px;color:var(--ink);font-size:15px;font-weight:620}
.empty p{margin-top:5px;font-size:12.5px}
.empty button{
  margin-top:18px;height:34px;padding:0 14px;
  border:1px solid var(--line-strong);border-radius:8px;
  background:var(--surface);color:var(--ink);font-size:12.5px;cursor:pointer;
}
.empty button:hover{border-color:var(--blue);color:var(--blue)}
.sentinel{
  display:flex;align-items:center;justify-content:center;gap:12px;
  min-height:82px;
  color:var(--faint);font-size:11.5px;letter-spacing:.02em;
}
.sentinel::before,.sentinel::after{
  content:"";width:34px;height:1px;background:var(--line);
}
.sentinel.is-done{color:var(--faint)}
.noscript{margin:24px 0;color:var(--muted);font-size:13px;text-align:center}

/* ---------------- about ---------------- */
.about{padding-top:clamp(58px,8vw,92px)}
.about-head h2{
  font-size:clamp(24px,3vw,34px);
  line-height:1.2;letter-spacing:-.045em;font-weight:680;
}
.about-grid{
  display:grid;grid-template-columns:repeat(3,minmax(0,1fr));
  margin-top:26px;
  border-top:1px solid var(--line);border-bottom:1px solid var(--line);
}
.about-grid article{padding:25px 27px 28px}
.about-grid article+article{border-left:1px solid var(--line)}
.num{
  display:block;margin-bottom:11px;
  font-family:var(--mono);font-size:10px;letter-spacing:.12em;color:var(--blue);
}
.about-grid h3{font-size:14px;font-weight:640;letter-spacing:-.015em}
.about-grid p{margin-top:6px;color:var(--muted);font-size:12.5px;line-height:1.75}

/* ---------------- footer ---------------- */
.footer{
  margin-top:clamp(56px,8vw,92px);
  padding:36px 0 38px;
  border-top:1px solid var(--line);
}
.footer-main{display:flex;align-items:flex-start;justify-content:space-between;gap:36px;flex-wrap:wrap}
.footer-brand{display:flex;align-items:center;gap:10px}
.footer-brand img{width:26px;height:26px}
.footer-brand strong{font-size:13.5px;font-weight:650;letter-spacing:-.01em}
.footer-brand p{margin-top:2px;color:var(--muted);font-size:11.5px}
.footer-links{display:flex;align-items:center;gap:22px;flex-wrap:wrap;padding-top:5px}
.footer-links a{color:var(--ink-2);font-size:12px;transition:color .18s ease}
.footer-links a:hover{color:var(--blue)}
.footer-bottom{
  display:flex;align-items:center;justify-content:space-between;gap:14px;flex-wrap:wrap;
  margin-top:28px;padding-top:17px;
  border-top:1px solid var(--line);
  color:var(--faint);font-size:11px;
}
.to-top{
  position:fixed;right:20px;bottom:20px;z-index:50;
  width:40px;height:40px;display:grid;place-items:center;padding:0;
  border:1px solid var(--line);border-radius:10px;
  background:var(--surface);color:var(--ink-2);cursor:pointer;
  opacity:0;pointer-events:none;transform:translateY(8px);
  transition:opacity .2s ease,transform .2s ease,border-color .2s ease,color .2s ease;
}
.to-top:hover{border-color:var(--blue);color:var(--blue)}
.to-top.is-on{opacity:1;pointer-events:auto;transform:none}

/* ---------------- responsive ---------------- */
@media (max-width:1100px){
  .grid{grid-template-columns:repeat(3,minmax(0,1fr))}
}
@media (max-width:880px){
  .grid{grid-template-columns:repeat(2,minmax(0,1fr))}
  .about-grid{grid-template-columns:1fr}
  .about-grid article{padding-inline:22px}
  .about-grid article+article{border-left:0;border-top:1px solid var(--line)}
}
@media (max-width:760px){
  :root{--header-h:60px}
  .topnav{display:none}
  .top-actions{margin-left:auto}
  .hero{padding-top:58px}
  .hero h1{font-size:clamp(40px,10.2vw,58px)}
  .lead{font-size:14.5px}
  .search{margin-top:28px}
  .dir-head{align-items:flex-start;flex-direction:column;gap:8px}
  .result-count{padding-bottom:0}
  .filters{gap:7px;padding:10px 0}
  .chip{height:36px;padding:0 12px;font-size:13px}
  .chip .n{font-size:10px}
  .filters{mask-image:linear-gradient(to right,#000 calc(100% - 40px),transparent)}
  .filters{-webkit-mask-image:linear-gradient(to right,#000 calc(100% - 40px),transparent)}
}
@media (max-width:560px){
  .brand-cn{display:none}
  .gh{display:none}
  .topbar-inner{gap:14px}
  .theme-switch button{width:27px}
  .hero{padding-top:50px;padding-bottom:40px}
  .eyebrow{font-size:9.5px;letter-spacing:.08em}
  .hero h1{font-size:clamp(37px,11.6vw,50px);letter-spacing:-.055em}
  .lead{font-size:14px;line-height:1.75}
  .search{height:54px;border-radius:14px;padding-left:14px}
  .keyhint{display:none}
  .hot{margin-top:10px}
  .hero-meta{gap:9px;margin-top:22px}
  .grid{grid-template-columns:1fr;gap:12px;margin-top:18px}
  .site{min-height:94px;padding:16px 14px;gap:13px}
  .site-mark{flex-basis:44px;width:44px;height:44px}
  .site-name{font-size:14px}
  .site-desc{font-size:11.8px;-webkit-line-clamp:2}
  .about-grid article{padding:22px 18px 24px}
  .footer-main{gap:22px}
  .footer-links{gap:16px}
  .footer-bottom{flex-direction:column;align-items:flex-start;gap:6px}
  .to-top{right:14px;bottom:14px;width:38px;height:38px}
}
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important}
}