/* ==========================================================================
   layout.css — 页面骨架 / 导航 / 章节 / 接入区
   ========================================================================== */

main{position:relative;z-index:1}

/* ---------- 导航 ---------- */
.nav{
  position:fixed;
  inset:0 0 auto 0;
  z-index:60;
  height:var(--nav-h);
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:18px;
  padding:0 clamp(14px,3vw,38px);
  background:linear-gradient(180deg,rgba(13,13,13,.92),rgba(13,13,13,.42) 70%,transparent);
  border-bottom:1px solid transparent;
  transition:background .4s var(--e-out),border-color .4s var(--e-out),height .4s var(--e-out);
}
.nav.is-stuck{
  background:rgba(13,13,13,.92);
  border-bottom-color:var(--ln-2);
  backdrop-filter:blur(14px) saturate(140%);
  -webkit-backdrop-filter:blur(14px) saturate(140%);
  height:56px;
}
/* 官网标志性顶部细黄线 */
.nav.is-stuck::after{
  content:'';
  position:absolute;left:0;bottom:-1px;height:3px;width:100%;
  background:var(--yl-1);
  animation:navSweep 4.5s var(--e-io) infinite;
}
@keyframes navSweep{
  0%{transform:scaleX(0);transform-origin:0 50%;opacity:0}
  35%{transform:scaleX(1);transform-origin:0 50%;opacity:1}
  100%{transform:scaleX(0);transform-origin:100% 50%;opacity:0}
}

.nav__logo{display:flex;align-items:center;gap:11px;flex:0 0 auto}
.nav__glyph{width:30px;height:30px;color:var(--yl-1);animation:spinGlyph 26s linear infinite}
@keyframes spinGlyph{to{transform:rotate(360deg)}}
.nav__text{display:flex;flex-direction:column;line-height:1.15}
.nav__text b{
  font-family:var(--f-head);
  font-size:15.5px;font-weight:700;letter-spacing:.22em;color:var(--tx-0);
}
.nav__text i{
  font-family:var(--f-mono);font-style:normal;
  font-size:9px;letter-spacing:.24em;color:var(--yl-3);
}

.nav__links{display:flex;align-items:center;gap:clamp(6px,1.6vw,26px)}
.nav__links a{
  position:relative;
  font-family:var(--f-head);
  font-size:13px;
  letter-spacing:.2em;
  color:var(--tx-2);
  padding:6px 2px;
  transition:color .3s var(--e-out);
}
.nav__links a::after{
  content:'';
  position:absolute;left:0;right:0;bottom:0;height:1px;
  background:var(--yl-1);
  transform:scaleX(0);transform-origin:50% 50%;
  transition:transform .35s var(--e-out);
}
.nav__links a:hover,.nav__links a.is-active{color:var(--yl-0)}
.nav__links a:hover::after,.nav__links a.is-active::after{transform:scaleX(1)}

.nav__right{display:flex;align-items:center;gap:10px}
.nav__btn{
  display:inline-flex;align-items:center;gap:8px;
  padding:7px 14px;
  font-family:var(--f-mono);font-size:11px;letter-spacing:.14em;
  color:var(--yl-1);
  background:rgba(255,250,0,.05);
  border:1px solid var(--ln-1);
  cursor:pointer;
  transition:border-color .3s var(--e-out),background .3s var(--e-out),color .3s var(--e-out);
}
.nav__btn:hover{border-color:var(--ln-0);background:rgba(255,250,0,.12);color:#fff}
.nav__btn-k{color:var(--tx-3)}
.nav__btn-v{color:var(--yl-0);font-weight:500}
.nav__btn--cta{
  font-family:var(--f-head);font-size:12.5px;font-weight:600;letter-spacing:.22em;
  color:#191919;background:var(--yl-1);border-color:transparent;
}
.nav__btn--cta:hover{background:#fff;color:#191919}

.nav__burger{display:none;width:38px;height:34px;padding:0;background:none;border:1px solid var(--ln-1);cursor:pointer}
.nav__burger i{display:block;width:16px;height:1px;margin:4px auto;background:var(--yl-1);transition:transform .3s var(--e-out),opacity .3s}
.nav__burger.is-on i:nth-child(1){transform:translateY(5px) rotate(45deg)}
.nav__burger.is-on i:nth-child(2){opacity:0}
.nav__burger.is-on i:nth-child(3){transform:translateY(-5px) rotate(-45deg)}

/* ---------- HERO ---------- */
.hero{
  position:relative;
  z-index:2;
  min-height:100svh;
  display:flex;
  flex-direction:column;
  justify-content:center;
  padding:calc(var(--nav-h) + 6vh) var(--gut) 12vh;
  pointer-events:none;
}
.hero>*{pointer-events:auto}

.hero__copy{
  max-width:min(560px,52vw);
  position:relative;
  z-index:3;
}
.hero__eyebrow{
  display:flex;align-items:center;gap:10px;
  font-family:var(--f-mono);
  font-size:11px;
  letter-spacing:.3em;
  color:var(--yl-1);
  margin-bottom:clamp(14px,2vh,26px);
  text-transform:uppercase;
}
.hero__eyebrow .dot{
  width:6px;height:6px;background:var(--yl-1);border-radius:50%;
  box-shadow:0 0 12px 2px rgba(255,250,0,.9);
  animation:pulseDot 2.4s var(--e-io) infinite;
}
@keyframes pulseDot{0%,100%{opacity:1;transform:scale(1)}50%{opacity:.35;transform:scale(.7)}}

.hero__title{position:relative;margin-bottom:clamp(16px,2.4vh,30px)}
/* 主标题采用官网 SubpageHeader 的白底黑字大标题块 */
.hero__title-cn{
  display:block;
  font-family:var(--f-head);
  font-size:clamp(52px,10.5vw,132px);
  font-weight:700;
  line-height:.95;
  letter-spacing:.06em;
  color:var(--bk-3);
  background:#fff;
  padding:.04em .18em .08em .1em;
  width:max-content;
  max-width:100%;
  box-sizing:border-box;
}
.hero__title-en{
  display:inline-block;
  margin-top:10px;
  font-family:var(--f-display);
  font-size:clamp(11px,1.4vw,15px);
  font-weight:500;
  letter-spacing:.5em;
  text-transform:uppercase;
  color:var(--bk-3);
  background:var(--yl-1);
  padding:4px 12px;
}
/* 官网色带：洋红 / 青绿 / 主黄 */
.hero__title::before{
  content:'';
  position:absolute;left:-2px;bottom:-18px;width:min(392px,72%);height:4px;
  background:linear-gradient(90deg,var(--mg-1) 0 33.3%,var(--gn-1) 0 66.6%,var(--yl-1) 0);
}

.hero__lede{
  font-size:clamp(13.5px,1.15vw,16px);
  line-height:2;
  color:var(--tx-1);
  max-width:46ch;
  margin-bottom:clamp(20px,3vh,34px);
}
.hero__stats{
  display:flex;gap:clamp(14px,2.4vw,40px);flex-wrap:wrap;
  padding:16px 0;
  border-top:1px solid var(--ln-1);
  border-bottom:1px solid var(--ln-1);
  margin-bottom:clamp(22px,3vh,36px);
}
.hero__stats>div{display:flex;flex-direction:column;gap:4px}
.hero__stats b{
  font-family:var(--f-display);font-size:13.5px;font-weight:700;
  letter-spacing:.2em;color:var(--yl-1);
}
.hero__stats i{font-style:normal;font-size:11.5px;letter-spacing:.16em;color:var(--tx-3)}
.hero__cta{display:flex;gap:12px;flex-wrap:wrap}

.hero__scroll{
  position:absolute;left:50%;bottom:calc(var(--tel-h) + 18px);
  transform:translateX(-50%);
  display:flex;flex-direction:column;align-items:center;gap:10px;
  font-family:var(--f-mono);font-size:9.5px;letter-spacing:.4em;color:var(--tx-3);
}

/* 竖屏/窄屏时模型位于文字后方，用底部渐隐遮罩保证可读性 */
.hero__scrim{
  position:absolute;
  inset:auto 0 0 0;
  height:74%;
  z-index:1;
  pointer-events:none;
  opacity:0;
  background:linear-gradient(180deg,
    transparent 0%,
    rgba(13,13,13,.45) 14%,
    rgba(13,13,13,.86) 34%,
    rgba(13,13,13,.97) 58%,
    rgba(13,13,13,1) 100%);
}
@media (max-width:980px){
  .hero__scrim{opacity:1}
}
.hero__scroll i{
  display:block;width:1px;height:52px;
  background:linear-gradient(180deg,var(--yl-1),transparent);
  position:relative;overflow:hidden;
}
.hero__scroll i::after{
  content:'';position:absolute;left:0;top:-52px;width:1px;height:52px;
  background:linear-gradient(180deg,transparent,#fff);
  animation:scrollTrail 2.6s var(--e-io) infinite;
}
@keyframes scrollTrail{to{top:52px}}

/* ---------- 章节 ---------- */
.sec{
  position:relative;
  z-index:2;
  padding:var(--sec-y) 0;
}
.sec--alt{
  background:linear-gradient(180deg,rgba(19,19,21,.99),rgba(19,19,21,1) 12%,rgba(19,19,21,1) 88%,rgba(19,19,21,.99));
  border-top:1px solid var(--ln-2);
  border-bottom:1px solid var(--ln-2);
}
.sec::before{
  content:'';
  position:absolute;left:0;top:0;width:100%;height:1px;
  background:linear-gradient(90deg,transparent,var(--ln-1) 20%,var(--ln-1) 80%,transparent);
  opacity:.6;
}
.sec--alt::before,.sec--alt+.sec::before{opacity:0}

/* ---------- 接入区 ---------- */
.access{
  position:relative;
  z-index:2;
  padding:clamp(70px,11vh,150px) var(--gut);
  text-align:center;
  background:
    radial-gradient(700px 320px at 50% 50%, rgba(255,250,0,.14), transparent 70%),
    linear-gradient(180deg,transparent,rgba(13,13,13,.9));
}
.access__box{
  max-width:760px;margin:0 auto;
  padding:clamp(30px,5vw,64px) clamp(22px,4vw,54px);
  border:1px solid var(--ln-1);
  background:rgba(19,19,21,.6);
  backdrop-filter:blur(8px);
  -webkit-backdrop-filter:blur(8px);
  position:relative;
  clip-path:polygon(22px 0,100% 0,100% calc(100% - 22px),calc(100% - 22px) 100%,0 100%,0 22px);
}
.access__eyebrow{
  font-family:var(--f-mono);font-size:10px;letter-spacing:.4em;
  color:var(--mg-1);margin-bottom:16px;
}
.access h2{
  font-size:clamp(26px,4vw,46px);
  letter-spacing:.14em;
  margin-bottom:18px;
  text-shadow:0 0 40px rgba(255,250,0,.4);
}
.access p{color:var(--tx-2);font-size:14px;line-height:2;margin-bottom:30px}
.access__acts{display:flex;gap:12px;justify-content:center;flex-wrap:wrap}

/* ---------- 内容淡出（模型为主要视觉时的页面基调） ---------- */
.hero,.sec,.access{will-change:opacity}