@import url('https://fonts.googleapis.com/css2?family=Open+Sans:wght@300;400;500;600;700&family=Poppins:wght@400;500;600;700&display=swap');

:root{
  --ink:#000000;
  --paper:#ffffff;
  --line:rgba(0,0,0,.14);
  --soft:rgba(0,0,0,.045);
  --maxw:1240px;
  --radius:28px;
  --pad:clamp(1rem,5vw,2.5rem);
  --sans:'Open Sans','PingFang SC','Hiragino Sans GB','Microsoft YaHei',system-ui,sans-serif;
  --head:'Poppins','PingFang SC','Microsoft YaHei',system-ui,sans-serif;
}

*,*::before,*::after{box-sizing:border-box}

html{
  scroll-behavior:smooth;
  -webkit-text-size-adjust:100%;
}
html.locked{overflow:hidden}

body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:var(--sans);
  font-size:16px;
  line-height:1.7;
  overflow-x:hidden;
  -webkit-font-smoothing:antialiased;
}

h1,h2,h3,h4,h5{
  font-family:var(--head);
  line-height:1.16;
  letter-spacing:-.01em;
  margin:0 0 .55em;
  font-weight:700;
}

p{margin:0 0 1.1em}
a{color:inherit;text-decoration:none}
img{display:block;max-width:100%;height:auto}
ul,ol{padding-left:1.25em}
hr{border:0;border-top:2px solid var(--ink);margin:0 0 1.3rem}
small{font-size:.8rem}

:focus-visible{outline:2px solid var(--ink);outline-offset:3px}
.hero :focus-visible,.foot :focus-visible,.menu-close:focus-visible{outline-color:currentColor}

[id]{scroll-margin-top:150px}

/* ---- 顶栏 ---- */
.topbar{
  position:sticky;
  top:0;
  z-index:50;
  background:rgba(255,255,255,.88);
  -webkit-backdrop-filter:blur(16px) saturate(140%);
  backdrop-filter:blur(16px) saturate(140%);
  border-bottom:1px solid var(--ink);
}

.masthead{
  display:grid;
  grid-template-columns:1fr auto 1fr;
  align-items:center;
  gap:.4rem;
  padding:.45rem clamp(.7rem,3vw,1.4rem);
}

.menu-btn{
  grid-column:1;
  justify-self:start;
  display:inline-flex;
  flex-direction:column;
  justify-content:center;
  gap:5px;
  width:46px;
  height:46px;
  padding:0 11px;
  background:transparent;
  border:1px solid var(--ink);
  border-radius:999px;
  cursor:pointer;
}
.menu-btn span{display:block;height:2px;background:var(--ink)}
.menu-btn span:last-child{width:58%}

.brand{
  grid-column:2;
  justify-self:center;
  font-family:var(--head);
  font-weight:700;
  font-size:clamp(1.1rem,4.4vw,1.55rem);
  letter-spacing:.14em;
  padding:.6rem .4rem;
  white-space:nowrap;
}

.cta{
  grid-column:3;
  justify-self:end;
  display:inline-flex;
  align-items:center;
  min-height:44px;
  padding:.65rem 1rem;
  background:var(--ink);
  color:var(--paper);
  border-radius:999px;
  font-size:.85rem;
  font-weight:600;
  letter-spacing:.04em;
  transition:transform .2s ease,opacity .2s ease;
}
.cta:hover{transform:translateY(-1px);opacity:.88}

/* ---- 粘性锚点条 ---- */
.strip{padding:.1rem clamp(.5rem,3vw,1rem) .5rem}
.strip-in{display:block}
.strip nav ul{
  display:flex;
  gap:.35rem;
  margin:0;
  padding:.1rem 0;
  list-style:none;
  overflow-x:auto;
  scrollbar-width:none;
  justify-content:flex-start;
}
.strip nav ul::-webkit-scrollbar{display:none}
.strip nav a{
  display:inline-flex;
  align-items:center;
  min-height:40px;
  padding:.3rem .82rem;
  border:1px solid var(--line);
  border-radius:999px;
  font-size:.82rem;
  white-space:nowrap;
  transition:background .2s ease,color .2s ease,border-color .2s ease;
}
.strip nav a:hover,.strip nav a:focus-visible{background:var(--ink);color:var(--paper);border-color:var(--ink)}

/* ---- 全屏遮罩菜单 ---- */
.menu{
  position:fixed;
  inset:0;
  z-index:60;
  display:grid;
  place-items:center;
  padding:5.2rem 1.2rem 2rem;
  background:rgba(255,255,255,.94);
  -webkit-backdrop-filter:blur(20px);
  backdrop-filter:blur(20px);
  opacity:0;
  visibility:hidden;
  transition:opacity .3s ease,visibility .3s ease;
}
.menu.open{opacity:1;visibility:visible}
.menu nav{width:100%;max-width:560px}
.menu nav ul{list-style:none;margin:0;padding:0;display:grid;gap:0}
.menu nav li{border-top:1px solid var(--line)}
.menu nav li:first-child{border-top:2px solid var(--ink)}
.menu nav a{
  display:block;
  padding:.95rem .2rem;
  min-height:48px;
  font-family:var(--head);
  font-size:clamp(1.1rem,4.6vw,1.4rem);
  font-weight:600;
}
.menu nav a:hover{text-decoration:underline;text-underline-offset:6px}
.menu-close{
  position:fixed;
  top:1rem;
  right:1rem;
  z-index:61;
  width:46px;
  height:46px;
  border:1px solid var(--ink);
  border-radius:999px;
  background:var(--paper);
  color:var(--ink);
  font-size:1.1rem;
  cursor:pointer;
}

/* ---- 首屏 ---- */
.hero{
  position:relative;
  isolation:isolate;
  display:grid;
  align-items:end;
  min-height:70vh;
  padding:clamp(2.2rem,9vw,5rem) var(--pad) clamp(1.6rem,4vw,3rem);
  background:var(--ink);
  color:var(--paper);
  overflow:hidden;
}
.hero-fig{position:absolute;inset:0;margin:0;z-index:-1}
.hero-fig img{
  width:100%;
  height:100%;
  object-fit:cover;
  opacity:.42;
  filter:grayscale(1) contrast(1.08);
  transform:scale(1.1);
  will-change:transform;
}
.hero-copy{width:100%;max-width:var(--maxw);margin:0 auto;text-align:right}
.hero h1{
  font-size:clamp(2rem,8.5vw,4.6rem);
  line-height:1.06;
  letter-spacing:-.025em;
  margin:0 0 .5em;
  text-wrap:balance;
}
.hero-desc{
  max-width:36ch;
  margin:0 0 0 auto;
  font-size:clamp(.95rem,2.4vw,1.08rem);
  color:rgba(255,255,255,.82);
}
.hero-desc::before{
  content:"";
  display:block;
  width:64px;
  height:2px;
  background:var(--paper);
  margin:0 0 1rem auto;
}

/* ---- 主体栅格 ---- */
.stage{
  display:grid;
  grid-template-columns:1fr;
  gap:clamp(1.5rem,4vw,2.5rem);
  max-width:var(--maxw);
  margin:0 auto;
  padding:clamp(2rem,6vw,4.5rem) var(--pad);
}

.rail{
  border-top:3px solid var(--ink);
  padding-top:.9rem;
}
.rail h2{
  font-size:.92rem;
  letter-spacing:.2em;
  margin:0 0 .7rem;
}
.rail hr{margin:0 0 .2rem;border-top-width:1px}
.rail-list{list-style:none;margin:0;padding:0;font-size:.9rem}
.rail-list li+li{border-top:1px solid var(--line)}
.rail-list a{display:block;padding:.5rem 0;min-height:40px;line-height:1.5}
.rail-list a:hover{text-decoration:underline;text-underline-offset:4px}

.stage-body{min-width:0;font-size:1.02rem}
.stage-body article{margin-bottom:2.3rem}
.stage-body h2{font-size:clamp(1.5rem,4.8vw,2.25rem);margin-top:2.2rem}
.stage-body h3{font-size:clamp(1.15rem,3.2vw,1.4rem);margin-top:1.7rem}
.stage-body hr{border-top:1px solid rgba(0,0,0,.35);margin:1.6rem 0}
.stage-body p{margin-bottom:1.05em}
.stage-body a{text-decoration:underline;text-underline-offset:3px;text-decoration-thickness:1px}
.stage-body ul,.stage-body ol{margin:0 0 1.2em}
.stage-body li{margin-bottom:.45em}
.stage-body img{border-radius:10px;margin:1.4rem 0}
.stage-body figure{margin:1.8rem 0}
.stage-body figcaption{font-size:.82rem;letter-spacing:.04em;color:#333;padding-top:.5rem;border-top:1px solid var(--line)}
.stage-body blockquote{
  margin:2rem 0;
  padding:1.3rem 1.5rem;
  border-left:6px solid var(--ink);
  border-radius:0 18px 18px 0;
  background:var(--soft);
  font-family:var(--head);
  font-size:clamp(1.05rem,3vw,1.35rem);
  line-height:1.45;
}
.stage-body blockquote p:last-child{margin-bottom:0}
.stage-body strong{font-weight:700}
.stage-body table{width:100%;border-collapse:collapse;margin:1.5rem 0;font-size:.95rem}
.stage-body th,.stage-body td{border-bottom:1px solid var(--line);padding:.55rem .4rem;text-align:left}

/* ---- 回到顶部 ---- */
.totop-wrap{display:flex;justify-content:center;max-width:var(--maxw);margin:0 auto;padding:0 var(--pad) 3rem}
.totop{
  display:inline-flex;
  align-items:center;
  min-height:44px;
  padding:.7rem 1.5rem;
  border:1px solid var(--ink);
  border-radius:999px;
  font-size:.9rem;
  transition:background .2s ease,color .2s ease;
}
.totop:hover{background:var(--ink);color:var(--paper)}

/* ---- 页脚 ---- */
.foot{
  display:grid;
  grid-template-columns:1fr;
  gap:1.4rem;
  padding:clamp(2.4rem,7vw,4rem) var(--pad) 2rem;
  background:var(--ink);
  color:var(--paper);
}
.foot-brand{
  margin:0;
  font-family:var(--head);
  font-weight:700;
  font-size:clamp(2.6rem,11vw,6rem);
  line-height:.88;
  letter-spacing:-.035em;
}
.foot-tags{
  display:flex;
  flex-wrap:wrap;
  gap:.2rem 1.1rem;
  margin:0;
  font-size:.88rem;
  color:rgba(255,255,255,.78);
}
.foot-tags a{display:inline-flex;align-items:center;min-height:40px;padding:.3rem 0}
.foot-tags a:hover{color:var(--paper);text-decoration:underline;text-underline-offset:4px}
.foot-note{margin:0;font-size:.88rem;color:rgba(255,255,255,.7)}
.foot small{
  grid-column:1/-1;
  padding-top:1rem;
  border-top:1px solid rgba(255,255,255,.28);
  color:rgba(255,255,255,.58);
}

/* ---- 动效 ---- */
.reveal{opacity:0;transform:translateY(18px);transition:opacity .6s ease,transform .6s ease}
.reveal.in{opacity:1;transform:none}

@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .reveal{opacity:1;transform:none}
  *,*::before,*::after{transition-duration:.01ms!important;animation-duration:.01ms!important}
}

/* ---- 断点 ---- */
@media (min-width:640px){
  .foot{grid-template-columns:1.3fr 1fr}
  .foot-brand{grid-column:1/-1}
  .foot small{grid-column:1/-1}
}

@media (min-width:900px){
  .masthead{padding:.55rem 1.6rem}
  .strip{padding:.15rem 1.6rem .6rem}
  .strip nav ul{justify-content:center;flex-wrap:wrap;overflow:visible}
  .stage{grid-template-columns:230px minmax(0,1fr);gap:clamp(2rem,5vw,4rem);align-items:start}
  .rail{position:sticky;top:150px}
  .stage-body > article:first-of-type > p:first-of-type::first-letter{
    float:left;
    font-family:var(--head);
    font-weight:700;
    font-size:3.5rem;
    line-height:.8;
    padding:.14em .1em 0 0;
  }
}

@media (min-width:1040px){
  .foot{grid-template-columns:1.4fr 1fr 1fr}
  .foot-brand{grid-column:1}
  .foot small{grid-column:1/-1}
}

@media (min-width:1120px){
  .stage-body{columns:2;column-gap:3rem;column-rule:1px solid var(--line)}
  .stage-body h2,.stage-body h3,.stage-body figure,.stage-body blockquote,.stage-body table{break-inside:avoid}
}

button[aria-expanded]{min-width:44px;min-height:44px}