/* 颐学云 — design tokens, base, typography, layout, chrome
   B2B editorial system. No gradients-as-decoration, no glow, no glass. */

:root{
  /* Ink / neutrals (cool gray) */
  --ink:#14171C;
  --ink-2:#3B414B;
  --ink-3:#697079;
  --ink-4:#9AA1AB;
  --paper:#FFFFFF;
  --surface:#F6F7F9;
  --surface-2:#EDF0F4;
  --surface-3:#E4E8EE;
  --line:#E3E6EB;
  --line-2:#D2D7DE;

  /* Brand — deep editorial blue (trust / platform) */
  --brand:#1F4FA3;
  --brand-strong:#163A78;
  --brand-600:#2A5FBE;
  --brand-tint:#ECF1FA;
  --brand-tint-2:#DBE6F7;

  /* AI — warm amber, used ONLY for AI content */
  --ai:#B45616;
  --ai-strong:#8F4310;
  --ai-tint:#FBF0E4;
  --ai-tint-2:#F4DFC9;

  /* Status */
  --ok:#1C7A52;
  --ok-tint:#E6F2EC;
  --warn:#B4530E;
  --danger:#B42318;
  --danger-tint:#FBEDEC;

  /* Radius */
  --r-xs:6px;
  --r-sm:9px;
  --r-md:12px;
  --r-lg:16px;
  --r-xl:22px;
  --r-pill:999px;

  /* Shadow — subtle only */
  --sh-1:0 1px 2px rgba(20,23,28,.05), 0 1px 3px rgba(20,23,28,.05);
  --sh-2:0 2px 6px rgba(20,23,28,.06), 0 6px 16px rgba(20,23,28,.07);
  --sh-3:0 8px 28px rgba(20,23,28,.10), 0 2px 8px rgba(20,23,28,.06);
  --sh-card:0 1px 0 rgba(20,23,28,.04), 0 4px 14px rgba(20,23,28,.06);

  /* Layout */
  --maxw:1200px;
  --maxw-wide:1320px;
  --gutter:clamp(20px,5vw,48px);
  --nav-h:64px;

  --font-sans:"IBM Plex Sans","PingFang SC","Hiragino Sans GB","Microsoft YaHei",-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;
  --font-cjk:"PingFang SC","Hiragino Sans GB","Microsoft YaHei","IBM Plex Sans",-apple-system,sans-serif;
  --font-mono:"IBM Plex Mono",ui-monospace,SFMono-Regular,Menlo,monospace;
}

*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth;scroll-padding-top:calc(var(--nav-h) + 16px)}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}
body{
  margin:0;
  font-family:var(--font-sans);
  background:var(--paper);
  color:var(--ink);
  font-size:16px;
  line-height:1.6;
  letter-spacing:-0.003em;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
  overflow-x:hidden;
}
img,svg,video{display:block;max-width:100%}
a{color:inherit;text-decoration:none}
button{font-family:inherit}
::selection{background:var(--brand-tint-2);color:var(--brand-strong)}

/* ---------- Typography ---------- */
h1,h2,h3,h4{margin:0;font-weight:600;line-height:1.12;letter-spacing:-0.022em;color:var(--ink);text-wrap:balance}
p{margin:0;text-wrap:pretty}

.display{font-size:clamp(2.5rem,5.4vw,4.1rem);font-weight:600;line-height:1.05;letter-spacing:-0.03em}
.h1{font-size:clamp(2.05rem,3.6vw,3rem);line-height:1.08}
.h2{font-size:clamp(1.65rem,2.6vw,2.25rem)}
.h3{font-size:clamp(1.2rem,1.6vw,1.4rem);letter-spacing:-0.018em}
.h4{font-size:1.0625rem;font-weight:600;letter-spacing:-0.01em}

.lead{font-size:clamp(1.075rem,1.45vw,1.28rem);line-height:1.55;color:var(--ink-2);font-weight:400}
.body-lg{font-size:1.0625rem;color:var(--ink-2)}
.muted{color:var(--ink-3)}
.small{font-size:.875rem}
.mono{font-family:var(--font-mono);font-feature-settings:"tnum" 1}

.eyebrow{
  display:inline-flex;align-items:center;gap:8px;
  font-size:.78rem;font-weight:600;letter-spacing:.08em;text-transform:uppercase;
  color:var(--brand);
}
.eyebrow.ai{color:var(--ai)}
.eyebrow::before{content:"";width:18px;height:1.5px;background:currentColor;opacity:.6}

/* ---------- Layout ---------- */
.container{width:100%;max-width:var(--maxw);margin-inline:auto;padding-inline:var(--gutter)}
.container-wide{max-width:var(--maxw-wide)}
.container-narrow{max-width:760px}
.section{padding-block:clamp(56px,8vw,104px)}
.section-sm{padding-block:clamp(40px,5vw,64px)}
.section.tint{background:var(--surface)}
.section.ink{background:var(--ink);color:#EAECEF}
.section.ink h1,.section.ink h2,.section.ink h3{color:#fff}
.divider{height:1px;background:var(--line);border:0}

.grid{display:grid;gap:24px}
.flow > * + *{margin-top:var(--flow,1rem)}
.stack{display:flex;flex-direction:column;gap:var(--gap,16px)}
.row{display:flex;align-items:center;gap:var(--gap,12px)}
.wrap{flex-wrap:wrap}

/* ---------- Buttons ---------- */
.btn{
  --bg:var(--ink);--fg:#fff;--bd:var(--ink);
  display:inline-flex;align-items:center;justify-content:center;gap:8px;
  padding:11px 19px;border-radius:var(--r-sm);
  font-size:.95rem;font-weight:600;letter-spacing:-0.01em;
  background:var(--bg);color:var(--fg);border:1px solid var(--bd);
  cursor:pointer;transition:background .16s ease,border-color .16s ease,transform .08s ease,box-shadow .16s ease;
  white-space:nowrap;
}
.btn:hover{transform:translateY(-1px)}
.btn:active{transform:translateY(0)}
.btn svg{width:17px;height:17px}
.btn.primary{--bg:var(--brand);--bd:var(--brand);--fg:#fff;box-shadow:var(--sh-1)}
.btn.primary:hover{--bg:var(--brand-600);--bd:var(--brand-600)}
.btn.dark{--bg:var(--ink);--bd:var(--ink)}
.btn.dark:hover{--bg:#262b33;--bd:#262b33}
.btn.ghost{--bg:transparent;--fg:var(--ink);--bd:var(--line-2)}
.btn.ghost:hover{--bg:var(--surface);--bd:var(--ink-4)}
.btn.on-ink.ghost{--fg:#fff;--bd:rgba(255,255,255,.28)}
.btn.on-ink.ghost:hover{--bg:rgba(255,255,255,.08)}
.btn.lg{padding:14px 26px;font-size:1.02rem;border-radius:var(--r-md)}
.btn.sm{padding:8px 14px;font-size:.875rem}
.btn:focus-visible{outline:2.5px solid var(--brand-600);outline-offset:2px}

.link-arrow{display:inline-flex;align-items:center;gap:6px;font-weight:600;color:var(--brand);font-size:.95rem}
.link-arrow svg{width:16px;height:16px;transition:transform .16s ease}
.link-arrow:hover svg{transform:translateX(3px)}
.link-arrow.ai{color:var(--ai)}

/* ---------- Badges / pills ---------- */
.badge{display:inline-flex;align-items:center;gap:6px;padding:4px 10px;border-radius:var(--r-pill);
  font-size:.78rem;font-weight:600;border:1px solid var(--line-2);background:var(--paper);color:var(--ink-2);white-space:nowrap}
.badge.brand{background:var(--brand-tint);border-color:var(--brand-tint-2);color:var(--brand-strong)}
.badge.ai{background:var(--ai-tint);border-color:var(--ai-tint-2);color:var(--ai-strong)}
.badge.ok{background:var(--ok-tint);border-color:#CDE6D9;color:var(--ok)}
.badge svg{width:13px;height:13px}

.tag{font-size:.74rem;font-weight:600;letter-spacing:.04em;color:var(--ink-3);text-transform:uppercase}

/* ---------- Card ---------- */
.card{background:var(--paper);border:1px solid var(--line);border-radius:var(--r-md);box-shadow:var(--sh-card)}
.card.pad{padding:24px}
.card.flat{box-shadow:none}
.card-hover{transition:transform .18s ease,box-shadow .18s ease,border-color .18s ease}
.card-hover:hover{transform:translateY(-3px);box-shadow:var(--sh-2);border-color:var(--line-2)}

/* icon chip */
.ichip{display:inline-flex;align-items:center;justify-content:center;width:42px;height:42px;border-radius:10px;
  background:var(--brand-tint);color:var(--brand);border:1px solid var(--brand-tint-2)}
.ichip svg{width:21px;height:21px;stroke-width:1.7}
.ichip.ai{background:var(--ai-tint);color:var(--ai);border-color:var(--ai-tint-2)}
.ichip.neutral{background:var(--surface-2);color:var(--ink-2);border-color:var(--line)}
.ichip.lg{width:52px;height:52px;border-radius:12px}
.ichip.lg svg{width:26px;height:26px}

/* ---------- Header / nav ---------- */
.site-header{position:sticky;top:0;z-index:80;height:var(--nav-h);
  display:flex;align-items:center;
  background:rgba(255,255,255,.72);backdrop-filter:saturate(140%) blur(12px);
  border-bottom:1px solid transparent;transition:border-color .2s,background .2s,box-shadow .2s}
.site-header.solid{background:rgba(255,255,255,.92);border-bottom-color:var(--line);box-shadow:0 1px 0 rgba(20,23,28,.02)}
.nav{display:flex;align-items:center;justify-content:space-between;width:100%;max-width:var(--maxw-wide);
  margin-inline:auto;padding-inline:var(--gutter);gap:20px}
.brand{display:flex;align-items:center;gap:10px;font-weight:600;font-size:1.075rem;letter-spacing:-0.02em;color:var(--ink)}
.brand .logomark{width:30px;height:30px;flex:none}
.brand .brand-logo{height:34px;width:auto;max-width:none;flex:none;object-fit:contain}
.nav-links{display:flex;align-items:center;gap:2px}
.nav-item{position:relative}
.nav-link{display:inline-flex;align-items:center;gap:5px;padding:8px 13px;border-radius:8px;
  font-size:.95rem;font-weight:500;color:var(--ink-2);cursor:pointer;transition:background .14s,color .14s}
.nav-link:hover,.nav-item.open .nav-link{background:var(--surface-2);color:var(--ink)}
.nav-link .chev{width:14px;height:14px;transition:transform .2s}
.nav-item.open .chev{transform:rotate(180deg)}
.nav-cta{display:flex;align-items:center;gap:10px}

/* mega menu */
.mega{position:absolute;top:calc(100% + 10px);left:50%;transform:translateX(-50%) translateY(6px);
  min-width:560px;background:var(--paper);border:1px solid var(--line);border-radius:var(--r-lg);
  box-shadow:var(--sh-3);padding:14px;opacity:0;visibility:hidden;transition:opacity .18s,transform .18s;z-index:90}
.nav-item.open .mega{opacity:1;visibility:visible;transform:translateX(-50%) translateY(0)}
.mega-grid{display:grid;grid-template-columns:1fr 1fr;gap:6px}
.mega-link{display:flex;gap:12px;padding:12px;border-radius:10px;transition:background .14s}
.mega-link:hover{background:var(--surface)}
.mega-link .ichip{width:36px;height:36px;border-radius:9px}
.mega-link .ichip svg{width:18px;height:18px}
.mega-link h5{margin:0 0 2px;font-size:.95rem;font-weight:600;color:var(--ink)}
.mega-link p{font-size:.83rem;color:var(--ink-3);line-height:1.4}

.hamburger{display:none;width:42px;height:42px;border:1px solid var(--line);border-radius:9px;background:var(--paper);
  align-items:center;justify-content:center;cursor:pointer}
.hamburger svg{width:20px;height:20px}

/* mobile drawer */
.drawer-scrim{position:fixed;inset:0;background:rgba(20,23,28,.4);z-index:95;opacity:0;visibility:hidden;transition:opacity .2s}
.drawer-scrim.open{opacity:1;visibility:visible}
.drawer{position:fixed;top:0;right:0;height:100dvh;width:min(360px,86vw);background:var(--paper);z-index:96;
  transform:translateX(100%);transition:transform .26s cubic-bezier(.4,0,.2,1);display:flex;flex-direction:column;
  box-shadow:var(--sh-3);overflow-y:auto}
.drawer.open{transform:translateX(0)}
.drawer-head{display:flex;align-items:center;justify-content:space-between;padding:16px var(--gutter);border-bottom:1px solid var(--line)}
.drawer-body{padding:12px var(--gutter) 28px;display:flex;flex-direction:column;gap:2px}
.drawer-body .d-link{padding:13px 8px;font-size:1.05rem;font-weight:500;border-bottom:1px solid var(--line);color:var(--ink)}
.drawer-body .d-sub{font-size:.78rem;font-weight:600;letter-spacing:.06em;text-transform:uppercase;color:var(--ink-4);padding:18px 8px 6px}
.drawer-body .d-link.child{padding-left:18px;font-weight:400;color:var(--ink-2);font-size:.98rem}
.drawer-cta{display:flex;flex-direction:column;gap:10px;margin-top:18px}

/* ---------- Footer ---------- */
.site-footer{background:var(--ink);color:#B7BDC6;padding-block:clamp(48px,6vw,72px) 28px;font-size:.92rem}
.site-footer a{color:#B7BDC6;transition:color .14s}
.site-footer a:hover{color:#fff}
.footer-grid{display:grid;grid-template-columns:1.4fr repeat(4,1fr);gap:40px 32px}
.footer-brand .brand{color:#fff;margin-bottom:14px}
.footer-brand .footer-logo{display:inline-flex;margin-bottom:20px}
.footer-brand .footer-logo .brand-logo{height:38px;filter:saturate(.95) brightness(1.05);opacity:.96}
.footer-brand p{color:#8C939D;max-width:30ch;font-size:.9rem}
.footer-col h5{color:#fff;font-size:.82rem;font-weight:600;letter-spacing:.05em;text-transform:uppercase;margin:0 0 16px}
.footer-col ul{list-style:none;margin:0;padding:0;display:flex;flex-direction:column;gap:11px}
.footer-bottom{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:16px;
  margin-top:44px;padding-top:24px;border-top:1px solid rgba(255,255,255,.1);color:#8C939D;font-size:.85rem}
.footer-bottom .fb-links{display:flex;flex-wrap:wrap;gap:18px}
.qr-row{display:flex;gap:14px;margin-top:18px}
.qr{width:64px;text-align:center;color:#8C939D;font-size:.72rem}
.qr .qr-box{width:64px;height:64px;border-radius:8px;background:#23272F;border:1px solid rgba(255,255,255,.08);
  display:flex;align-items:center;justify-content:center;margin-bottom:6px}
.qr .qr-box svg{width:30px;height:30px;color:#5A626C}

/* ---------- Floating: chat + cookie ---------- */
.chat-fab{position:fixed;right:24px;bottom:24px;z-index:70;display:flex;align-items:center;gap:9px;
  padding:12px 18px 12px 14px;border-radius:var(--r-pill);background:var(--ink);color:#fff;
  box-shadow:var(--sh-3);cursor:pointer;font-weight:600;font-size:.92rem;border:1px solid #2a2f38;
  transition:transform .16s}
.chat-fab:hover{transform:translateY(-2px)}
.chat-fab svg{width:19px;height:19px}
.chat-panel{position:fixed;right:24px;bottom:24px;z-index:71;width:min(360px,92vw);background:var(--paper);
  border:1px solid var(--line);border-radius:var(--r-lg);box-shadow:var(--sh-3);overflow:hidden;
  transform:translateY(12px) scale(.98);opacity:0;visibility:hidden;transition:all .2s;transform-origin:bottom right}
.chat-panel.open{transform:none;opacity:1;visibility:visible}
.chat-head{background:var(--brand);color:#fff;padding:16px 18px}
.chat-head h5{color:#fff;margin:0 0 2px}
.chat-head p{font-size:.82rem;color:rgba(255,255,255,.82)}
.chat-body{padding:18px}
.chat-field{width:100%;padding:11px 13px;border:1px solid var(--line-2);border-radius:9px;font-family:inherit;
  font-size:.92rem;margin-bottom:10px;background:var(--paper);color:var(--ink)}
textarea.chat-field{resize:vertical;min-height:78px}
.chat-field:focus{outline:2px solid var(--brand-600);outline-offset:0;border-color:transparent}

.cookie-bar{position:fixed;left:24px;bottom:24px;z-index:69;max-width:440px;background:var(--paper);
  border:1px solid var(--line);border-radius:var(--r-md);box-shadow:var(--sh-3);padding:18px 20px;
  display:flex;flex-direction:column;gap:13px;transition:transform .3s,opacity .3s}
.cookie-bar.hide{transform:translateY(20px);opacity:0;visibility:hidden}
.cookie-bar p{font-size:.86rem;color:var(--ink-2)}
.cookie-bar .row{justify-content:flex-end;gap:10px}

/* ---------- Forms ---------- */
.field{display:flex;flex-direction:column;gap:6px}
.field label{font-size:.85rem;font-weight:600;color:var(--ink-2)}
.field .req{color:var(--danger)}
.input,.select,.textarea{width:100%;padding:11px 13px;border:1px solid var(--line-2);border-radius:9px;
  font-family:inherit;font-size:.95rem;background:var(--paper);color:var(--ink);transition:border-color .14s,box-shadow .14s}
.textarea{resize:vertical;min-height:96px}
.input:focus,.select:focus,.textarea:focus{outline:none;border-color:var(--brand-600);box-shadow:0 0 0 3px var(--brand-tint)}
.field-row{display:grid;grid-template-columns:1fr 1fr;gap:16px}

/* ---------- Scroll reveal ---------- */
.reveal{opacity:0;transform:translateY(14px);transition:opacity .5s cubic-bezier(.4,0,.2,1),transform .5s cubic-bezier(.4,0,.2,1)}
.reveal.in{opacity:1;transform:none}
.reveal[data-d="1"]{transition-delay:.06s}
.reveal[data-d="2"]{transition-delay:.12s}
.reveal[data-d="3"]{transition-delay:.18s}
.reveal[data-d="4"]{transition-delay:.24s}
@media (prefers-reduced-motion:reduce){.reveal{opacity:1;transform:none;transition:none}}
/* JS 不可用（含部分爬虫渲染器）时不隐藏内容 */
@media (scripting:none){.reveal{opacity:1;transform:none}}

/* ---------- helpers ---------- */
.center{text-align:center}
.mx-auto{margin-inline:auto}
.maxw-prose{max-width:62ch}
.hide-mobile{}
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);border:0}
:focus-visible{outline:2.5px solid var(--brand-600);outline-offset:2px;border-radius:3px}

/* ---------- responsive nav ---------- */
@media (max-width:980px){
  .nav-links,.nav-cta .btn.ghost{display:none}
  .hamburger{display:inline-flex}
  .footer-grid{grid-template-columns:1fr 1fr}
  .footer-brand{grid-column:1 / -1}
}
@media (max-width:640px){
  .field-row{grid-template-columns:1fr}
  .footer-grid{grid-template-columns:1fr 1fr;gap:30px 20px}
  .nav-cta .btn.ghost{display:none !important}
  .chat-fab{right:16px;bottom:16px;width:48px;height:48px;padding:0;justify-content:center}
  .chat-fab span{display:none}
  .cookie-bar{
    left:16px;
    right:16px;
    bottom:76px;
    max-width:none;
    padding:14px 16px;
    gap:10px;
  }
  .cookie-bar p{font-size:.8rem;line-height:1.55}
  .cookie-bar .row{justify-content:flex-end}
}