@import url('https://fonts.googleapis.com/css2?family=Press+Start+2P&family=VT323&display=swap');

:root{
  --ink:#171f26;
  --ink-up:#1d2833;
  --ink-dn:#141b22;
  --ice:#c8e0f4;
  --pink:#f5e0e8;
  --txt:#dbe8f2;
  --dim:#93a9ba;
  --sh-d:rgba(5,9,13,.72);
  --sh-l:rgba(200,224,244,.09);
  --r1:12px; --r2:16px; --r3:28px;
  --pix:'Press Start 2P',ui-monospace,monospace;
  --mono:'VT323',ui-monospace,monospace;
  --body:system-ui,-apple-system,'PingFang SC','Hiragino Sans GB','Microsoft YaHei',sans-serif;
  --ease:cubic-bezier(.2,.7,.3,1);
  --raise:-5px -5px 14px var(--sh-l),5px 5px 16px var(--sh-d);
  --raise-lg:-8px -8px 22px var(--sh-l),8px 8px 26px var(--sh-d);
  --sink:inset -3px -3px 9px var(--sh-l),inset 3px 3px 9px var(--sh-d);
}

*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth;overflow-x:hidden;-webkit-text-size-adjust:100%}
body{
  margin:0;min-height:100vh;background:var(--ink);color:var(--txt);
  font-family:var(--body);font-size:17px;line-height:1.75;
  -webkit-font-smoothing:antialiased;
}
body::before{
  content:"";position:fixed;inset:0;z-index:0;pointer-events:none;
  background:
    radial-gradient(62vw 55vw at 92% 4%,rgba(200,224,244,.13),transparent 68%),
    radial-gradient(58vw 52vw at 2% 94%,rgba(245,224,232,.10),transparent 70%);
}
img{max-width:100%;height:auto}
p{margin:0 0 1em}
ul,ol{margin:0 0 1em;padding-left:1.15em}
li{margin:.35em 0}
a{color:var(--ice);text-underline-offset:3px}
:focus-visible{outline:2px solid var(--pink);outline-offset:3px}

/* ---------- 左侧固定竖排导航 ---------- */
.rail{
  position:fixed;inset:0 auto 0 0;width:242px;z-index:40;
  display:flex;flex-direction:column;gap:20px;
  padding:24px 18px 26px;overflow:hidden;
  background:linear-gradient(148deg,#1c2732,#151c23);
  box-shadow:8px 0 26px rgba(4,7,11,.6);
}
.brand{
  display:flex;align-items:center;gap:10px;
  padding:10px 12px;min-height:48px;
  border-radius:var(--r2);text-decoration:none;
  background:linear-gradient(145deg,#1f2b37,#161e26);
  box-shadow:var(--raise);
  transition:box-shadow .18s var(--ease),transform .18s var(--ease);
}
.brand:active{transform:scale(.98);box-shadow:var(--sink)}
.brand-mark{
  flex:0 0 auto;width:26px;height:26px;border-radius:8px;
  display:grid;place-items:center;
  font-family:var(--mono);font-size:20px;line-height:1;color:var(--ink);
  background:linear-gradient(145deg,#e2f0fa,#c2dcf0);
  box-shadow:0 0 12px rgba(200,224,244,.35);
}
.brand-txt{
  font-size:15px;font-weight:700;letter-spacing:.08em;color:var(--ice);
  white-space:nowrap;overflow:hidden;text-overflow:ellipsis;
}
.nav{flex:1 1 auto;min-height:0;overflow:auto;overscroll-behavior:contain}
.menu{list-style:none;margin:0;padding:0;display:flex;flex-direction:column;gap:10px}
.m-link{
  position:relative;display:flex;align-items:center;
  min-height:44px;padding:10px 15px;
  border-radius:var(--r2);text-decoration:none;color:var(--txt);
  font-size:15px;letter-spacing:.02em;
  background:linear-gradient(145deg,var(--ink-up),#161e26);
  box-shadow:var(--raise);
  transition:box-shadow .16s var(--ease),color .16s var(--ease),transform .16s var(--ease);
}
.m-link:hover{color:#fff;box-shadow:var(--sink)}
.m-link:active{transform:scale(.975)}
.m-link.is-on{
  color:#15202a;
  background:linear-gradient(145deg,#dceefb,#bfdaee);
  box-shadow:-4px -4px 10px rgba(200,224,244,.22),4px 4px 12px rgba(4,8,12,.62);
}
.grp{display:flex;flex-direction:column;gap:8px}
.grp>a::after{
  content:"▾";margin-left:auto;font-size:11px;color:var(--dim);
  transition:transform .2s var(--ease);
}
.grp:hover>a::after,.grp:focus-within>a::after{transform:translateY(2px);color:var(--ice)}
.sub{
  list-style:none;margin:0 0 0 12px;padding:0;
  display:flex;flex-direction:column;gap:8px;
  max-height:0;overflow:hidden;
  transition:max-height .3s var(--ease);
}
.grp:hover .sub,.grp:focus-within .sub{max-height:220px}
.sub .m-link{font-size:14px;min-height:40px;padding-left:20px;border-radius:var(--r1)}
.cta{
  display:flex;align-items:center;justify-content:center;
  min-height:46px;padding:12px 16px;border-radius:var(--r2);
  font-size:15px;font-weight:700;letter-spacing:.06em;text-decoration:none;
  color:#16202a;background:linear-gradient(145deg,#d8ebf9,#bdd8ed);
  box-shadow:-5px -5px 14px rgba(200,224,244,.16),5px 5px 16px rgba(4,8,12,.66);
  transition:transform .15s var(--ease),box-shadow .15s var(--ease);
}
.cta:active{transform:scale(.97);box-shadow:var(--sink)}
.burger{display:none}

/* ---------- 主区 ---------- */
main{position:relative;z-index:1;margin-left:242px;padding:0 clamp(16px,3vw,40px)}

.hero{
  position:relative;min-height:70vh;margin:24px 0 34px;
  display:flex;align-items:flex-end;justify-content:flex-end;
  padding:clamp(22px,4vw,54px);
  border-radius:var(--r3);overflow:hidden;
  background:linear-gradient(150deg,#243240,#171f26);
  box-shadow:var(--raise-lg);
}
.hero-media{position:absolute;inset:0;margin:0;overflow:hidden}
.hero-media img{width:100%;height:100%;object-fit:cover;display:block;transform:scale(1.06)}
.hero-media::after{
  content:"";position:absolute;inset:0;
  background:linear-gradient(258deg,rgba(23,31,38,.34),rgba(23,31,38,.88) 66%);
}
.hero-copy{
  position:relative;z-index:2;max-width:38ch;
  display:flex;flex-direction:column;align-items:flex-end;gap:14px;text-align:right;
}
.hero-badge{
  font-family:var(--mono);font-size:17px;line-height:1.4;letter-spacing:.16em;
  padding:6px 15px;border-radius:12px;color:#1a242e;
  background:linear-gradient(145deg,#f9e9ef,#efd8e2);
  box-shadow:-3px -3px 10px rgba(245,224,232,.28),4px 4px 14px rgba(4,8,12,.6);
}
h1{
  margin:0;font-size:clamp(26px,3.5vw,44px);line-height:1.34;font-weight:800;
  letter-spacing:.01em;color:#f3f9fe;
  text-shadow:0 6px 22px rgba(3,6,9,.66),0 1px 0 rgba(255,255,255,.06);
}
.hero-lead{max-width:32ch;margin:0;color:#c4d5e2;font-size:16px;line-height:1.7}

.body{
  display:grid;grid-template-columns:216px minmax(0,1fr);
  gap:clamp(18px,2.6vw,36px);align-items:start;padding-bottom:56px;
}
.toc{
  position:sticky;top:26px;padding:16px 12px;
  border-radius:var(--r3);
  background:linear-gradient(148deg,#1c2732,#161e25);
  box-shadow:var(--raise);
}
.toc ul{list-style:none;margin:0;padding:0;display:flex;flex-direction:column;gap:6px}
.toc a{
  display:flex;align-items:center;gap:10px;min-height:42px;padding:8px 11px;
  border-radius:var(--r1);text-decoration:none;font-size:14px;color:var(--dim);
  transition:color .16s var(--ease),box-shadow .16s var(--ease);
}
.toc a:hover{color:var(--ice);box-shadow:var(--sink)}
.toc a.is-on{color:var(--ice);box-shadow:var(--sink)}
.toc .n{font-family:var(--pix);font-size:9px;letter-spacing:.05em;opacity:.62}

.prose{min-width:0}
.eyebrow{
  display:block;margin:4px 0 8px;font-size:13px;letter-spacing:.28em;
  color:var(--pink);text-transform:none;
}
.prose-h{margin:0 0 24px;font-size:clamp(22px,2.6vw,30px);line-height:1.4;color:#eef7fe}
.prose>section{
  margin:0 0 26px;padding:clamp(20px,3vw,34px);
  border-radius:var(--r3);
  background:linear-gradient(150deg,#1d2731,#161d24);
  box-shadow:-7px -7px 20px var(--sh-l),7px 7px 22px var(--sh-d);
  scroll-margin-top:26px;
}
.prose section h2{
  margin:0 0 14px;font-size:clamp(20px,2.3vw,26px);line-height:1.42;color:#edf6fd;
}
.prose section h3{margin:22px 0 10px;font-size:18px;line-height:1.5;color:var(--ice)}
.prose section small{
  display:block;margin-bottom:8px;font-size:13px;letter-spacing:.22em;color:var(--pink);
}
.prose section p{color:#cddce8}
.prose section strong{color:#f2f9ff}
.prose figure{margin:18px 0}
.prose figure img{border-radius:var(--r2);box-shadow:var(--raise)}
.prose figcaption{font-size:13px;color:var(--dim);margin-top:8px}
.prose blockquote{
  margin:18px 0;padding:14px 18px;border-radius:var(--r2);
  box-shadow:var(--sink);color:#dbe9f4;
}
.prose table{width:100%;border-collapse:collapse;font-size:15px}
.prose th,.prose td{padding:10px 12px;text-align:left}
.prose tr{box-shadow:inset 0 -1px 0 rgba(200,224,244,.08)}

/* ---------- 页脚 ---------- */
.foot{
  position:relative;z-index:1;margin-left:242px;
  padding:34px clamp(16px,3vw,40px) 46px;
  display:flex;flex-wrap:wrap;align-items:baseline;justify-content:center;
  gap:6px 24px;text-align:center;
  box-shadow:inset 0 1px 0 rgba(200,224,244,.07);
}
.foot-brand{
  margin:0;font-size:clamp(36px,8vw,74px);line-height:1.05;font-weight:800;letter-spacing:-.01em;
  background:linear-gradient(145deg,#dcecf9,#f3dbe4);
  -webkit-background-clip:text;background-clip:text;
  -webkit-text-fill-color:transparent;color:transparent;
}
.foot-note{color:var(--dim);font-size:13px;letter-spacing:.14em}

.top{
  position:fixed;right:18px;bottom:18px;z-index:45;
  min-height:44px;padding:10px 16px;border:0;border-radius:14px;
  font-family:var(--body);font-size:14px;color:var(--txt);
  background:linear-gradient(148deg,#222f3c,#171f26);
  box-shadow:-4px -4px 12px var(--sh-l),5px 5px 14px rgba(4,8,12,.7);
  cursor:pointer;opacity:0;pointer-events:none;
  transition:opacity .22s var(--ease),transform .15s var(--ease);
}
.top.on{opacity:1;pointer-events:auto}
.top:active{transform:scale(.96);box-shadow:var(--sink)}

/* ---------- 移动端 ---------- */
@media (max-width:900px){
  .rail{
    inset:0 0 auto 0;width:auto;flex-direction:row;flex-wrap:wrap;align-items:center;
    gap:8px;padding:9px 12px;overflow:visible;
    border-radius:0 0 20px 20px;
    box-shadow:0 10px 26px rgba(4,7,11,.62);
  }
  .brand{flex:1 1 96px;min-height:42px;padding:8px 10px}
  .brand-txt{font-size:14px}
  .cta{min-height:42px;padding:10px 12px;font-size:13px;letter-spacing:.02em}
  .burger{
    display:grid;place-items:center;min-height:42px;min-width:52px;padding:10px 12px;
    border:0;border-radius:var(--r1);font-family:var(--body);font-size:13px;color:var(--txt);
    background:linear-gradient(145deg,#1f2b37,#161e26);box-shadow:var(--raise);cursor:pointer;
  }
  .burger:active{box-shadow:var(--sink);transform:scale(.97)}
  .nav{
    order:3;flex-basis:100%;max-height:0;overflow:hidden;
    transition:max-height .3s var(--ease);
  }
  .rail.is-open .nav{max-height:62vh;overflow:auto;padding-bottom:10px}
  .sub{max-height:none}
  .grp>a::after{content:"▾"}
  main,.foot{margin-left:0}
  main{padding-top:2px}
  .hero{min-height:62vh;margin:14px 0 24px;padding:20px 18px;justify-content:flex-end}
  .hero-copy{max-width:100%}
  h1{font-size:clamp(24px,7vw,32px)}
  .body{grid-template-columns:1fr;gap:20px;padding-bottom:36px}
  .toc{position:static;border-radius:var(--r3)}
  .toc ul{display:grid;grid-template-columns:1fr 1fr;gap:6px}
  .toc a{font-size:13px;min-height:42px;padding:8px 9px}
  .prose>section{scroll-margin-top:118px;margin-bottom:20px}
  .foot{padding:26px 16px 74px}
}

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

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