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

:root{
  --ink:#1f1f1f;
  --paper:#f5f5f5;
  --card:#ffffff;
  --line:#1f1f1f;
  --muted:#6e6e6e;
  --rad:28px;
  --gut:20px;
  --stick:128px;
}

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

html{
  scroll-behavior:smooth;
  -webkit-text-size-adjust:100%;
}

body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:'Space Grotesk',-apple-system,BlinkMacSystemFont,'PingFang SC','Hiragino Sans GB','Microsoft YaHei',sans-serif;
  font-size:17px;
  line-height:1.7;
  font-weight:400;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}

img{max-width:100%;height:auto;display:block}
a{color:inherit}
h1,h2,h3{line-height:1.12;letter-spacing:-.03em;margin:0}
p{margin:0 0 1em}
ul,ol{margin:0;padding:0;list-style:none}
button,input{font:inherit;color:inherit}
::selection{background:var(--ink);color:var(--paper)}

:focus-visible{
  outline:3px solid var(--ink);
  outline-offset:3px;
  border-radius:6px;
}

/* ---------- 顶部 ---------- */

.topbar{
  position:sticky;
  top:0;
  z-index:90;
  background:rgba(245,245,245,.95);
  backdrop-filter:blur(10px);
  -webkit-backdrop-filter:blur(10px);
  border-bottom:1.5px solid var(--ink);
}

.topbar-inner{
  display:grid;
  grid-template-columns:auto 1fr auto;
  align-items:center;
  gap:10px;
  padding:10px var(--gut);
}

.burger{
  display:inline-flex;
  align-items:center;
  gap:9px;
  min-height:44px;
  padding:9px 15px;
  border:1.5px solid var(--ink);
  border-radius:999px;
  background:var(--card);
  color:var(--ink);
  font-size:1rem;
  font-weight:600;
  cursor:pointer;
  transition:background .18s ease,color .18s ease;
}
.burger:hover{background:var(--ink);color:var(--paper)}
.burger:hover .burger-bars,
.burger:hover .burger-bars::before,
.burger:hover .burger-bars::after{background:var(--paper)}

.burger-bars{
  position:relative;
  display:block;
  width:17px;height:2px;
  background:var(--ink);
  transition:background .18s ease;
}
.burger-bars::before,
.burger-bars::after{
  content:"";
  position:absolute;left:0;
  width:17px;height:2px;
  background:var(--ink);
  transition:background .18s ease;
}
.burger-bars::before{top:-6px}
.burger-bars::after{top:6px}

.brand{
  justify-self:center;
  display:inline-flex;
  align-items:center;
  gap:8px;
  min-height:44px;
  padding:6px 8px;
  text-decoration:none;
  font-weight:700;
  font-size:1rem;
  letter-spacing:.01em;
  white-space:nowrap;
}
.brand-logo{width:26px;height:26px;object-fit:contain}
.brand:hover .brand-text{text-decoration:underline;text-underline-offset:4px;text-decoration-thickness:2px}

.topbar-jump{
  justify-self:end;
  display:inline-flex;
  align-items:center;
  min-height:44px;
  padding:9px 16px;
  border-radius:999px;
  background:var(--ink);
  color:var(--paper);
  font-size:1rem;
  font-weight:600;
  text-decoration:none;
  white-space:nowrap;
  transition:transform .18s ease;
}
.topbar-jump:hover{transform:translateY(-2px)}

.anchorbar{
  overflow-x:auto;
  border-top:1.5px solid var(--ink);
  transition:opacity .2s ease;
  scrollbar-width:none;
}
.anchorbar::-webkit-scrollbar{display:none}

.anchor-list{
  display:flex;
  gap:8px;
  padding:9px var(--gut);
  width:max-content;
  min-width:100%;
}
.anchor-list a{
  display:inline-flex;
  align-items:center;
  min-height:40px;
  padding:8px 15px;
  border:1.5px solid var(--ink);
  border-radius:999px;
  background:var(--card);
  text-decoration:none;
  font-size:1rem;
  white-space:nowrap;
  transition:background .18s ease,color .18s ease;
}
.anchor-list a:hover{background:var(--ink);color:var(--paper)}

/* ---------- 全屏菜单 ---------- */

.menu-panel{
  position:fixed;
  inset:0;
  z-index:60;
  overflow:auto;
  background:var(--paper);
  padding:104px var(--gut) 44px;
  opacity:0;
  visibility:hidden;
  transform:translateY(-12px);
  transition:opacity .24s ease,transform .24s ease,visibility .24s ease;
}
.menu-open{overflow:hidden}
.menu-open .menu-panel{opacity:1;visibility:visible;transform:none}
.menu-open .anchorbar{opacity:0;pointer-events:none}

.menu-nav{max-width:1100px;margin:0 auto}
.menu-list li{border-bottom:1.5px solid var(--ink)}
.menu-list li:first-child{border-top:1.5px solid var(--ink)}
.menu-list a{
  display:flex;
  align-items:center;
  min-height:62px;
  padding:16px 4px;
  text-decoration:none;
  font-size:clamp(1.35rem,5.4vw,2.2rem);
  font-weight:600;
  letter-spacing:-.035em;
  transition:padding-left .2s ease;
}
.menu-list a:hover{padding-left:16px;text-decoration:underline;text-underline-offset:6px;text-decoration-thickness:2px}

/* ---------- 首屏 ---------- */

.page{padding-bottom:36px}

.hero{
  min-height:70vh;
  display:flex;
  flex-direction:column;
  align-items:center;
  justify-content:center;
  gap:24px;
  text-align:center;
  padding:clamp(34px,8vh,88px) var(--gut) clamp(26px,5vh,54px);
}

.hero-mark{display:grid;place-items:center}
.hero-logo{width:66px;height:66px;object-fit:contain}
.hero-dot{
  display:block;
  width:62px;height:62px;
  border:3px solid var(--ink);
  border-radius:50%;
  position:relative;
}
.hero-dot::after{
  content:"";
  position:absolute;
  inset:16px;
  border-radius:50%;
  background:var(--ink);
}

.hero-title{
  font-size:clamp(2.6rem,9.4vw,6.2rem);
  font-weight:700;
  letter-spacing:-.045em;
  line-height:.94;
  max-width:17ch;
  margin:0;
  text-wrap:balance;
}

/* ---------- 正文骨架 ---------- */

.content-shell{
  max-width:1180px;
  margin:0 auto;
  padding:6px var(--gut) 56px;
  display:grid;
  gap:18px;
  grid-template-columns:minmax(0,1fr) 290px;
  grid-template-areas:
    "body rail"
    "fig rail";
  align-items:start;
}

.content-body{grid-area:body;min-width:0}

.content-body > section{
  background:var(--card);
  border:1.5px solid var(--line);
  border-radius:var(--rad);
  padding:clamp(20px,3.2vw,36px);
  margin-bottom:16px;
  overflow:hidden;
  scroll-margin-top:calc(var(--stick) + 12px);
  transition:transform .22s ease;
}
.content-body > section:hover{transform:scale(1.006)}

.content-body small{
  display:block;
  font-size:1rem;
  letter-spacing:.2em;
  color:var(--muted);
  margin-bottom:4px;
}

.content-body h2{
  font-size:clamp(1.5rem,3.4vw,2.1rem);
  font-weight:700;
  margin:0 0 14px;
}
.content-body h3{
  font-size:clamp(1.2rem,2.4vw,1.5rem);
  font-weight:600;
  margin:20px 0 10px;
}

.content-body p,
.content-body li{font-size:1.0625rem;line-height:1.78}

.content-body a{
  text-decoration:underline;
  text-underline-offset:3px;
  text-decoration-thickness:1.5px;
}
.content-body a:hover{background:var(--ink);color:var(--paper);text-decoration:none}

.content-body ul,
.content-body ol{margin:0 0 1em}
.content-body ul li,
.content-body ol li{position:relative;padding-left:24px;margin-bottom:9px}
.content-body ul li::before{
  content:"";
  position:absolute;
  left:2px;top:.7em;
  width:9px;height:9px;
  border:2px solid var(--ink);
  border-radius:50%;
}
.content-body ol{counter-reset:step}
.content-body ol li{counter-increment:step}
.content-body ol li::before{
  content:counter(step) ".";
  position:absolute;left:0;top:0;
  font-weight:700;
  line-height:1.78;
}

.content-body img,
.content-body figure img{
  border:1.5px solid var(--ink);
  border-radius:18px;
  margin:14px 0;
}
.content-body figure{margin:16px 0}
.content-body blockquote{
  margin:16px 0;
  padding:4px 0 4px 18px;
  border-left:4px solid var(--ink);
  font-weight:500;
}
.content-body hr{
  border:0;
  border-top:1.5px solid var(--ink);
  margin:22px 0;
}

/* ---------- 侧栏 ---------- */

.rail{
  grid-area:rail;
  position:sticky;
  top:calc(var(--stick) + 10px);
  background:var(--card);
  border:1.5px solid var(--line);
  border-radius:var(--rad);
  padding:22px 20px;
}
.rail small{
  display:block;
  font-size:1rem;
  letter-spacing:.2em;
  color:var(--muted);
}
.rail-title{
  font-size:1.35rem;
  font-weight:700;
  margin:4px 0 8px;
}
.rail-list li + li{border-top:1px solid #dedede}
.rail-list a{
  display:flex;
  align-items:center;
  min-height:44px;
  padding:10px 0;
  font-weight:600;
  text-decoration:none;
}
.rail-list a:hover{text-decoration:underline;text-underline-offset:4px;text-decoration-thickness:2px}

/* ---------- 图块 ---------- */

.shell-fig{
  grid-area:fig;
  margin:0;
  display:grid;
  place-items:center;
  min-height:150px;
  padding:22px;
  background:var(--card);
  border:1.5px solid var(--line);
  border-radius:var(--rad);
  overflow:hidden;
}
.fig-img{width:88px;height:88px;object-fit:contain}

/* ---------- 页脚 ---------- */

.foot{
  background:var(--ink);
  color:var(--paper);
  padding:36px max(var(--gut), calc((100% - 1180px) / 2)) 22px;
  display:grid;
  grid-template-columns:minmax(0,1fr) minmax(0,1.15fr);
  gap:26px 34px;
}

.foot small{
  display:block;
  font-size:1rem;
  letter-spacing:.2em;
  color:#b6b6b6;
}
.foot h3{
  font-size:1.3rem;
  font-weight:700;
  margin:4px 0 14px;
  color:var(--paper);
}

.sub-form{display:flex;flex-wrap:wrap;gap:8px}
.sub-form input{
  flex:1 1 150px;
  min-height:46px;
  padding:10px 16px;
  border-radius:999px;
  border:1.5px solid #707070;
  background:transparent;
  color:var(--paper);
  font-size:1rem;
}
.sub-form input::placeholder{color:#a8a8a8}
.sub-form button{
  min-height:46px;
  padding:10px 22px;
  border-radius:999px;
  border:1.5px solid var(--paper);
  background:var(--paper);
  color:var(--ink);
  font-size:1rem;
  font-weight:700;
  cursor:pointer;
  transition:background .18s ease,color .18s ease;
}
.sub-form button:hover{background:transparent;color:var(--paper)}

.foot-nav ul{display:flex;flex-wrap:wrap;gap:4px 18px}
.foot-nav a{
  display:inline-flex;
  align-items:center;
  min-height:40px;
  padding:6px 0;
  color:var(--paper);
  text-decoration:none;
  font-size:1rem;
}
.foot-nav a:hover{text-decoration:underline;text-underline-offset:4px;text-decoration-thickness:2px}

.foot-legal{
  grid-column:1 / -1;
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  justify-content:space-between;
  gap:12px;
  border-top:1px solid #4d4d4d;
  padding-top:16px;
}
.copy{margin:0;font-size:1rem;color:#c9c9c9}
.totop{
  display:inline-flex;
  align-items:center;
  min-height:40px;
  padding:6px 0;
  color:var(--paper);
  text-decoration:none;
  font-size:1rem;
}
.totop:hover{text-decoration:underline;text-underline-offset:4px}

/* ---------- 滚动出现 ---------- */

.reveal{
  opacity:0;
  transform:translateY(16px);
  transition:opacity .5s ease,transform .5s ease;
}
.reveal.is-in{opacity:1;transform:none}

/* ---------- 断点 ---------- */

@media (max-width:1000px){
  :root{--stick:116px}
  .content-shell{
    grid-template-columns:minmax(0,1fr);
    grid-template-areas:
      "body"
      "rail"
      "fig";
  }
  .rail{position:static}
  .foot{grid-template-columns:minmax(0,1fr)}
  .foot-legal{grid-column:auto}
}

@media (max-width:620px){
  :root{--stick:104px;--gut:16px}
  .hero{min-height:64vh;gap:18px}
  .hero-title{font-size:clamp(2.3rem,11vw,3.4rem)}
  .content-body > section{padding:20px 18px;margin-bottom:14px}
  .burger{padding:8px 13px}
  .burger-label{display:none}
  .topbar-jump{padding:9px 13px}
  .menu-panel{padding-top:88px}
}

@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{
    animation-duration:.001ms !important;
    transition-duration:.001ms !important;
  }
  .reveal{opacity:1;transform:none}
  .content-body > section:hover{transform:none}
}

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