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

:root{
  --ink:#000000;
  --paper:#ffffff;
  --line:rgba(0,0,0,.16);
  --gap:2rem;
}

*,*::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:"Noto Sans JP",system-ui,-apple-system,"Hiragino Kaku Gothic ProN","Microsoft YaHei",sans-serif;
  font-size:17px;
  line-height:1.8;
  font-weight:400;
  overflow-x:hidden;
}

h1,h2,h3,.brand,.footbrand,.navgrp summary{
  font-family:"Noto Serif JP","Noto Serif SC",serif;
  font-weight:600;
}

img{max-width:100%;height:auto}

.shell{
  max-width:1200px;
  margin:0 auto;
  padding:0 24px;
}

/* ---------- 头部 ---------- */

.masthead{
  position:sticky;
  top:0;
  z-index:60;
  background:rgba(255,255,255,.94);
  -webkit-backdrop-filter:saturate(1.2) blur(10px);
  backdrop-filter:saturate(1.2) blur(10px);
  border-bottom:1px solid var(--ink);
}

.brandrow{
  display:flex;
  align-items:baseline;
  gap:1rem;
  padding:1rem 0 .35rem;
}

.brand{
  font-size:1.5rem;
  letter-spacing:.06em;
  color:var(--ink);
  text-decoration:none;
  line-height:1.3;
  white-space:nowrap;
}

.brandline{
  flex:1;
  height:1px;
  background:var(--ink);
  transform:translateY(-.3rem);
}

.navrow{
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:1rem;
  flex-wrap:wrap;
  padding-bottom:.6rem;
  border-top:1px solid var(--line);
  padding-top:.35rem;
}

.mainnav{min-width:0}

.navlist{
  list-style:none;
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  margin:0;
  padding:0;
  gap:.1rem;
}

.navlist a,
.navgrp summary{
  display:inline-flex;
  align-items:center;
  min-height:44px;
  padding:.45rem .8rem;
  font-size:1rem;
  line-height:1.4;
  color:var(--ink);
  text-decoration:none;
  border-radius:4px;
  transition:background-color .2s ease,color .2s ease;
  cursor:pointer;
}

.navlist a:hover,
.navlist a:focus-visible,
.navgrp summary:hover{
  background:var(--ink);
  color:var(--paper);
}

.navgrp{position:relative}

.navgrp summary{
  list-style:none;
  gap:.45rem;
}

.navgrp summary::-webkit-details-marker{display:none}

.navgrp summary::after{
  content:"";
  width:6px;
  height:6px;
  border-right:1px solid currentColor;
  border-bottom:1px solid currentColor;
  transform:rotate(45deg) translateY(-2px);
  transition:transform .2s ease;
}

.navgrp details[open] summary{background:var(--ink);color:var(--paper)}
.navgrp details[open] summary::after{transform:rotate(-135deg) translateY(-2px)}

.navgrp ul{
  position:absolute;
  left:0;
  top:100%;
  z-index:70;
  min-width:11rem;
  margin:.25rem 0 0;
  padding:.3rem 0;
  list-style:none;
  background:var(--paper);
  border:1px solid var(--ink);
  border-radius:4px;
}

.navgrp ul a{
  display:flex;
  min-height:44px;
  padding:.45rem 1rem;
  border-radius:0;
  white-space:nowrap;
}

.cta{
  display:inline-flex;
  align-items:center;
  min-height:44px;
  padding:0 1.15rem;
  background:var(--ink);
  color:var(--paper);
  font-size:1rem;
  letter-spacing:.05em;
  text-decoration:none;
  border:1px solid var(--ink);
  border-radius:4px;
  transition:background-color .2s ease,color .2s ease;
  white-space:nowrap;
}

.cta:hover,.cta:focus-visible{background:var(--paper);color:var(--ink)}

/* ---------- 首屏 ---------- */

.hero{
  position:relative;
  display:grid;
  grid-template-columns:minmax(0,1fr) auto;
  align-items:end;
  gap:var(--gap);
  min-height:70vh;
  padding:4.5rem 0 3.25rem;
  text-align:right;
  border-bottom:1px solid var(--ink);
}

.hero h1{
  grid-column:1;
  margin:0;
  font-size:clamp(2.1rem,5.6vw,4.1rem);
  line-height:1.14;
  letter-spacing:.01em;
}

.heromark{
  grid-column:2;
  justify-self:end;
  width:88px;
  height:88px;
  color:var(--ink);
  margin-bottom:.5rem;
}

.hero::after{
  content:"";
  position:absolute;
  left:0;
  bottom:-1px;
  width:min(46%,320px);
  height:10px;
  background:var(--ink);
  transform:skewX(-28deg);
  transform-origin:left bottom;
}

/* ---------- 主体网格 ---------- */

.stage{
  display:grid;
  grid-template-columns:minmax(0,1fr) 232px;
  gap:var(--gap);
  align-items:start;
  padding:3rem 0 4.5rem;
}

.body{
  min-width:0;
  max-width:70ch;
  counter-reset:sec;
}

.body h2{
  font-size:clamp(1.35rem,2.4vw,1.72rem);
  line-height:1.45;
  letter-spacing:.01em;
  margin:0 0 .55rem;
}

.body .subtitle{
  max-width:56ch;
  margin:0 0 .5rem;
  padding-bottom:1.35rem;
  border-bottom:1px solid var(--ink);
  font-size:1rem;
  line-height:1.8;
}

.body > div{
  counter-increment:sec;
  margin-top:2.75rem;
  padding-top:2rem;
  border-top:1px solid var(--ink);
  scroll-margin-top:118px;
}

.body > div::before{
  content:counter(sec,decimal-leading-zero);
  display:block;
  margin-bottom:.85rem;
  font-size:.9rem;
  font-weight:500;
  letter-spacing:.22em;
}

.body h3{
  font-size:1.15rem;
  line-height:1.5;
  margin:1.75rem 0 .5rem;
}

.body p{margin:0 0 1.1rem}

.body ul,.body ol{
  margin:0 0 1.2rem;
  padding-left:1.35rem;
}

.body li{margin:.35rem 0}

.body a{
  color:var(--ink);
  text-decoration:underline;
  text-underline-offset:3px;
}

.body img{
  display:block;
  margin:1.5rem 0;
  border:1px solid var(--line);
}

.body blockquote{
  margin:1.5rem 0;
  padding:.4rem 0 .4rem 1.25rem;
  border-left:3px solid var(--ink);
}

.body table{
  width:100%;
  border-collapse:collapse;
  margin:1.5rem 0;
  font-size:1rem;
}

.body th,.body td{
  border:1px solid var(--line);
  padding:.6rem .75rem;
  text-align:left;
}

.body code,.body pre{
  font-family:ui-monospace,SFMono-Regular,Menlo,monospace;
  font-size:.95rem;
}

/* ---------- 侧栏 ---------- */

.side{
  position:sticky;
  top:132px;
  align-self:start;
  padding:1rem 1rem 1.1rem;
  border:1px solid var(--ink);
  border-radius:4px;
  background:rgba(255,255,255,.72);
  -webkit-backdrop-filter:blur(9px);
  backdrop-filter:blur(9px);
}

.side ul{
  list-style:none;
  margin:0;
  padding:0;
}

.side a{
  display:flex;
  align-items:center;
  min-height:40px;
  padding:.35rem .1rem;
  font-size:1rem;
  line-height:1.4;
  color:var(--ink);
  text-decoration:none;
  border-bottom:1px solid var(--line);
}

.side li:last-child a{border-bottom:0}
.side a:hover,.side a:focus-visible{text-decoration:underline}

/* ---------- 页脚 ---------- */

.sitefoot{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  justify-content:space-between;
  gap:1.5rem 2rem;
  padding:2.5rem 0 3rem;
  border-top:1px solid var(--ink);
}

.footbrand a{
  font-family:"Noto Serif JP","Noto Serif SC",serif;
  font-size:clamp(1.6rem,5vw,2.6rem);
  font-weight:600;
  line-height:1.1;
  letter-spacing:.04em;
  color:var(--ink);
  text-decoration:none;
}

.footnav dl{
  display:grid;
  grid-template-columns:repeat(2,minmax(0,1fr));
  gap:.1rem 1.75rem;
  margin:0;
}

.footnav dt,.footnav dd{margin:0}

.footnav a{
  display:inline-flex;
  align-items:center;
  min-height:40px;
  padding:.2rem 0;
  font-size:1rem;
  color:var(--ink);
  text-decoration:none;
}

.footnav a:hover,.footnav a:focus-visible{text-decoration:underline}

.copy{
  margin:0;
  font-size:1rem;
  white-space:nowrap;
}

/* ---------- 动效 ---------- */

.js .reveal{
  opacity:0;
  transform:translateY(14px);
  transition:opacity .45s ease,transform .45s ease;
}

.js .reveal.in{
  opacity:1;
  transform:none;
}

/* ---------- 断点 ---------- */

@media (max-width:900px){
  .stage{grid-template-columns:minmax(0,1fr)}
  .side{position:static;order:2;margin-top:.5rem}
  .body{max-width:none}
}

@media (max-width:640px){
  .shell{padding:0 16px}
  .brandrow{padding-top:.9rem}
  .brand{font-size:1.3rem}
  .navrow{gap:.5rem}
  .navlist{gap:0}
  .navlist a,.navgrp summary{padding:.45rem .6rem}
  .cta{padding:0 .9rem}
  .navgrp ul{
    position:static;
    min-width:0;
    margin:.25rem 0;
    padding:.25rem 0;
  }
  .navgrp ul a{white-space:normal}
  .hero{
    grid-template-columns:minmax(0,1fr) auto;
    min-height:0;
    padding:2.5rem 0 2.25rem;
    gap:1rem;
  }
  .heromark{width:56px;height:56px}
  .stage{padding:2rem 0 3rem}
  .body > div{padding-top:1.6rem;margin-top:2.1rem;scroll-margin-top:150px}
  .sitefoot{
    flex-direction:column;
    align-items:flex-start;
    gap:1.35rem;
    padding:2rem 0 2.5rem;
  }
  .footnav{width:100%}
  .copy{white-space:normal}
}

@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .js .reveal{opacity:1;transform:none;transition:none}
  .navlist a,.navgrp summary,.cta,.navgrp summary::after{transition:none}
}

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