/* ============================================================
   智界AI · 官网 + 登录
   设计语言参考 mingjingai.com：浅色 / Inter+PingFang / 蓝紫渐变
   主题色：linear-gradient(135deg,#667eea,#764ba2)
   ============================================================ */

/* ---------- Design tokens ---------- */
:root{
  --bg:#ffffff;
  --bg-soft:#f6f7fc;
  --bg-tint:#eef0fb;
  --ink:#17171f;
  --ink-2:#454553;
  --ink-3:#8b8b99;
  --line:#e9e9f2;
  --line-2:#dedeea;

  --primary:#667eea;
  --primary-2:#764ba2;
  --grad:linear-gradient(135deg,#667eea 0%,#764ba2 100%);
  --grad-soft:linear-gradient(135deg,rgba(102,126,234,.10),rgba(118,75,162,.10));
  --grad-line:linear-gradient(135deg,rgba(102,126,234,.28),rgba(118,75,162,.28));

  --green:#22c08a;
  --amber:#f5a524;
  --danger:#e5484d;

  --card-shadow:0 1px 2px rgba(23,23,31,.04),0 10px 30px rgba(23,23,31,.06);
  --card-shadow-lg:0 2px 6px rgba(23,23,31,.05),0 24px 60px rgba(23,23,31,.10);
  --ring:0 0 0 4px rgba(102,126,234,.18);

  --r-sm:10px;
  --r:16px;
  --r-lg:24px;
  --r-xl:32px;

  --container:1200px;
  --nav-h:68px;

  --font:'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI','PingFang SC','Microsoft YaHei',sans-serif;
  --ease:cubic-bezier(.22,.61,.36,1);
}

/* ---------- Reset ---------- */
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body{
  margin:0;font-family:var(--font);color:var(--ink-2);
  background:var(--bg);line-height:1.7;font-size:16px;
  -webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;
  overflow-x:hidden;
}
img,svg,video{max-width:100%;display:block}
a{color:inherit;text-decoration:none}
button{font-family:inherit;cursor:pointer;border:none;background:none}
h1,h2,h3,h4{margin:0;color:var(--ink);line-height:1.18;font-weight:700;letter-spacing:-.02em}
p{margin:0}
ul{margin:0;padding:0;list-style:none}
::selection{background:rgba(102,126,234,.22)}

/* ---------- Layout ---------- */
.container{width:100%;max-width:var(--container);margin:0 auto;padding:0 24px}
.section{padding:96px 0}
.section--soft{background:var(--bg-soft)}
.section-head{max-width:660px;margin:0 auto 56px;text-align:center}
.section-head--left{margin:0 0 44px;text-align:left}
.eyebrow{
  display:inline-flex;align-items:center;gap:8px;font-size:13px;font-weight:600;
  letter-spacing:.04em;color:var(--primary);text-transform:uppercase;margin-bottom:16px;
}
.eyebrow::before{content:"";width:22px;height:2px;border-radius:2px;background:var(--grad)}
.section-title{font-size:clamp(26px,3.4vw,36px)}
.section-desc{margin-top:16px;font-size:17px;color:var(--ink-2)}

/* ---------- Buttons ---------- */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:9px;
  font-weight:600;font-size:15px;line-height:1;padding:14px 26px;border-radius:999px;
  transition:transform .2s var(--ease),box-shadow .2s var(--ease),background .2s,color .2s,border-color .2s;
  white-space:nowrap;
}
.btn:active{transform:translateY(1px)}
.btn svg{width:18px;height:18px}
.btn--primary{
  background:var(--grad);color:#fff;
  box-shadow:0 8px 20px -6px rgba(102,126,234,.55);
}
.btn--primary:hover{box-shadow:0 14px 30px -8px rgba(102,126,234,.7);transform:translateY(-2px)}
.btn--ghost{
  background:#fff;color:var(--ink);border:1px solid var(--line-2);
}
.btn--ghost:hover{border-color:var(--primary);color:var(--primary);background:var(--bg-tint)}
.btn--soft{background:var(--bg-tint);color:var(--primary)}
.btn--soft:hover{background:var(--grad-soft)}
.btn--lg{padding:17px 34px;font-size:16px}
.btn--block{width:100%}
.btn[disabled]{opacity:.6;cursor:not-allowed;transform:none}
.link-arrow{display:inline-flex;align-items:center;gap:7px;font-weight:600;color:var(--primary)}
.link-arrow svg{width:16px;height:16px;transition:transform .2s var(--ease)}
.link-arrow:hover svg{transform:translateX(4px)}

/* ---------- Nav ---------- */
.nav{
  position:fixed;inset:0 0 auto 0;height:var(--nav-h);z-index:100;
  background:rgba(255,255,255,.82);backdrop-filter:saturate(180%) blur(14px);
  -webkit-backdrop-filter:saturate(180%) blur(14px);
  border-bottom:1px solid transparent;transition:border-color .3s,box-shadow .3s,background .3s;
}
.nav.scrolled{border-bottom-color:var(--line);box-shadow:0 4px 20px rgba(23,23,31,.05);background:rgba(255,255,255,.92)}
.nav__inner{height:100%;display:flex;align-items:center;justify-content:space-between;gap:24px}
.brand{display:flex;align-items:center;gap:11px;font-weight:700;font-size:18px;color:var(--ink);letter-spacing:-.02em}
.brand__mark{width:34px;height:34px;flex:none}
.brand__name b{background:var(--grad);-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent}
.nav__links{display:flex;align-items:center;gap:34px}
.nav__links a{font-size:15px;font-weight:500;color:var(--ink-2);position:relative;padding:4px 0;transition:color .2s}
.nav__links a::after{content:"";position:absolute;left:0;bottom:-2px;width:0;height:2px;border-radius:2px;background:var(--grad);transition:width .25s var(--ease)}
.nav__links a:hover,.nav__links a.active{color:var(--ink)}
.nav__links a:hover::after,.nav__links a.active::after{width:100%}
.nav__actions{display:flex;align-items:center;gap:14px}
.btn--login{padding:10px 18px;font-size:14px;color:var(--ink-2)}
.btn--login:hover{color:var(--primary)}
.btn--signup{padding:11px 22px;font-size:14px}
.nav__toggle{display:none;width:42px;height:42px;border-radius:12px;border:1px solid var(--line);align-items:center;justify-content:center}
.nav__toggle svg{width:22px;height:22px;color:var(--ink)}

/* mobile menu */
.nav__mobile{
  position:fixed;top:var(--nav-h);left:0;right:0;z-index:99;
  background:#fff;border-bottom:1px solid var(--line);box-shadow:var(--card-shadow);
  padding:14px 24px 22px;display:none;flex-direction:column;gap:6px;
}
.nav__mobile.open{display:flex}
.nav__mobile a{padding:13px 4px;font-weight:500;color:var(--ink-2);border-bottom:1px solid var(--line)}
.nav__mobile a:last-of-type{border-bottom:none}
.nav__mobile .btn{margin-top:10px}
.nav__mobile .row{display:flex;gap:12px}
.nav__mobile .row .btn{flex:1}

/* ---------- Footer ---------- */
.footer{background:#101019;color:#b9b9c8;padding:72px 0 34px}
.footer a{color:#b9b9c8;transition:color .2s}
.footer a:hover{color:#fff}
.footer__grid{display:grid;grid-template-columns:1.6fr 1fr 1fr 1.2fr;gap:48px}
.footer__brand .brand{color:#fff;margin-bottom:16px}
.footer__brand p{font-size:14.5px;line-height:1.8;color:#8f8fa3;max-width:320px}
.footer__social{display:flex;gap:12px;margin-top:20px}
.footer__social a{width:38px;height:38px;border-radius:11px;background:rgba(255,255,255,.06);display:flex;align-items:center;justify-content:center;transition:background .2s,transform .2s}
.footer__social a:hover{background:var(--grad);transform:translateY(-2px)}
.footer__social svg{width:18px;height:18px;color:#fff}
.footer h4{color:#fff;font-size:14px;letter-spacing:.02em;margin-bottom:18px;font-weight:600}
.footer__col ul li{margin-bottom:13px}
.footer__col a{font-size:14.5px}
.footer__bottom{
  margin-top:56px;padding-top:26px;border-top:1px solid rgba(255,255,255,.09);
  display:flex;justify-content:space-between;align-items:center;gap:16px;flex-wrap:wrap;font-size:13.5px;color:#7c7c90;
}
.footer__bottom .links{display:flex;gap:22px}

/* ---------- Reveal (fail-open) ---------- */
.reveal{opacity:0;transform:translateY(22px);transition:opacity .7s var(--ease),transform .7s var(--ease)}
.reveal.in{opacity:1;transform:none}
.reveal[data-d="1"]{transition-delay:.08s}
.reveal[data-d="2"]{transition-delay:.16s}
.reveal[data-d="3"]{transition-delay:.24s}
.reveal[data-d="4"]{transition-delay:.32s}
/* JS 关闭时全部可见 */
.no-js .reveal{opacity:1;transform:none}

/* ---------- Forms (login) ---------- */
.field{margin-bottom:18px}
.field__label{display:block;font-size:14px;font-weight:600;color:var(--ink);margin-bottom:8px}
.field__box{
  display:flex;align-items:center;gap:11px;padding:0 16px;height:52px;
  border:1.5px solid var(--line-2);border-radius:14px;background:#fff;
  transition:border-color .2s,box-shadow .2s;
}
.field__box:focus-within{border-color:var(--primary);box-shadow:var(--ring)}
.field__box.err{border-color:var(--danger)}
.field__box.ok{border-color:var(--green)}
.field__box svg{width:20px;height:20px;color:var(--ink-3);flex:none}
.field__box input{flex:1;border:none;outline:none;font-size:15px;font-family:inherit;color:var(--ink);background:transparent;min-width:0}
.field__box input::placeholder{color:#b4b4c2}
.field__pwd{position:relative}
.field__eye{width:36px;height:36px;display:flex;align-items:center;justify-content:center;color:var(--ink-3);border-radius:9px;transition:color .2s}
.field__eye:hover{color:var(--primary)}
.field__eye svg{width:20px;height:20px}
.field__msg{font-size:12.5px;color:var(--danger);margin-top:7px;min-height:0;display:none}
.field.err .field__msg{display:block}
.field__row{display:flex;justify-content:space-between;align-items:center;margin:2px 0 22px}
.check{display:flex;align-items:center;gap:9px;font-size:14px;color:var(--ink-2);cursor:pointer;user-select:none}
.check input{position:absolute;opacity:0;width:0;height:0}
.check__box{width:19px;height:19px;border:1.5px solid var(--line-2);border-radius:6px;display:flex;align-items:center;justify-content:center;transition:all .2s;flex:none}
.check__box svg{width:12px;height:12px;color:#fff;opacity:0;transform:scale(.5);transition:all .2s var(--ease)}
.check input:checked+.check__box{background:var(--grad);border-color:transparent}
.check input:checked+.check__box svg{opacity:1;transform:scale(1)}
.check a{color:var(--primary);font-weight:500}

/* toast */
.toast{
  position:fixed;top:24px;left:50%;transform:translateX(-50%) translateY(-140%);
  z-index:200;padding:14px 22px;border-radius:14px;background:#fff;box-shadow:var(--card-shadow-lg);
  display:flex;align-items:center;gap:11px;font-size:14.5px;font-weight:500;color:var(--ink);
  transition:transform .4s var(--ease);max-width:calc(100vw - 32px);
}
.toast.show{transform:translateX(-50%) translateY(0)}
.toast svg{width:20px;height:20px;flex:none}
.toast--ok svg{color:var(--green)}
.toast--err svg{color:var(--danger)}

/* ---------- Utilities ---------- */
.grad-text{background:var(--grad);-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent}
.center{text-align:center}
.mt-0{margin-top:0}

/* ---------- Responsive base ---------- */
@media (max-width:960px){
  .nav__links{display:none}
  .nav__toggle{display:flex}
  .section{padding:72px 0}
  .footer__grid{grid-template-columns:1fr 1fr;gap:40px 32px}
}
@media (max-width:560px){
  .section{padding:56px 0}
  .footer__grid{grid-template-columns:1fr}
  .footer__bottom{flex-direction:column;align-items:flex-start}
  .btn{width:100%;}
  .container{padding:0 18px}
}

@media (prefers-reduced-motion:reduce){
  *{animation-duration:.001ms!important;animation-iteration-count:1!important;transition-duration:.001ms!important;scroll-behavior:auto!important}
  .reveal{opacity:1;transform:none}
}