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

/* ============================================================
   JOINTTOP — Design System v2 · 简洁高级
   少即是多：大留白、大字号、少分隔线、几乎无装饰。
   强调色只在两三处出现。图片大而少。
   ============================================================ */

:root{
  --ink:        #0C1013;
  --ink-2:      #565E65;
  --ink-3:      #8C949B;
  --ink-4:      #B3B9BE;

  --paper:      #FFFFFF;
  --wash:       #F7F7F6;
  --navy:       #0C1013;

  --line:       #E6E7E7;
  --line-2:     #CDD0D1;
  --line-dark:  rgba(255,255,255,.14);

  --accent:     #09C797;

  --display: 'Archivo', 'IBM Plex Sans', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  --body:    'IBM Plex Sans', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  --mono:    'IBM Plex Mono', ui-monospace, 'SF Mono', Menlo, monospace;

  --gutter: 48px;
  --maxw:   1280px;
  --pad:    168px;
}

*,*::before,*::after{ box-sizing:border-box; }
html{ -webkit-text-size-adjust:100%; scroll-behavior:smooth; }

body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:var(--body);
  font-size:16px;
  font-weight:400;
  line-height:1.8;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}

img{ max-width:100%; display:block; }
a{ color:inherit; text-decoration:none; }

/* 中俄文放宽字距，Archivo 的紧字距只适合拉丁字母 */
html[data-lang="zh"] .h-display,
html[data-lang="zh"] .h-1,
html[data-lang="zh"] .h-2{ letter-spacing:0; }
html[data-lang="ru"] .h-display,
html[data-lang="ru"] .h-1{ letter-spacing:-.012em; }
html[data-lang="zh"] body{ line-height:1.9; }

/* ---------- 布局 ---------- */
.wrap{ max-width:var(--maxw); margin:0 auto; padding:0 var(--gutter); }
.wrap--narrow{ max-width:920px; }
.section{ padding:var(--pad) 0; }
.section--half{ padding:calc(var(--pad) * .58) 0; }
.section--wash{ background:var(--wash); }
.section--dark{ background:var(--navy); color:#fff; }

/* ---------- 字阶 ---------- */
.eyebrow{
  font-family:var(--mono);
  font-size:11px; font-weight:500;
  letter-spacing:.24em; text-transform:uppercase;
  color:var(--ink-3);
  margin:0 0 40px;
}
.section--dark .eyebrow{ color:rgba(255,255,255,.5); }

.h-display{
  font-family:var(--display); font-weight:500;
  font-size:clamp(40px, 5.2vw, 82px);
  line-height:1.08; letter-spacing:-.028em;
  margin:0; text-wrap:balance;
}
.h-1{
  font-family:var(--display); font-weight:500;
  font-size:clamp(32px, 3.6vw, 54px);
  line-height:1.16; letter-spacing:-.022em;
  margin:0; text-wrap:balance;
}
.h-2{
  font-family:var(--display); font-weight:500;
  font-size:clamp(24px, 2.2vw, 32px);
  line-height:1.26; letter-spacing:-.016em;
  margin:0; text-wrap:pretty;
}
.h-3{
  font-family:var(--display); font-weight:500;
  font-size:20px; line-height:1.4; letter-spacing:-.008em;
  margin:0;
}
.lede{
  font-size:20px; font-weight:300; line-height:1.7;
  color:var(--ink-2); max-width:56ch; margin:0;
}
.body{ font-size:16.5px; line-height:1.8; color:var(--ink-2); margin:0; max-width:60ch; }
.small{ font-size:13.5px; line-height:1.7; color:var(--ink-3); margin:0; }
.section--dark .lede,
.section--dark .body{ color:rgba(255,255,255,.66); }
.section--dark .small{ color:rgba(255,255,255,.44); }

.label{
  font-family:var(--mono); font-size:10.5px; font-weight:500;
  letter-spacing:.2em; text-transform:uppercase; color:var(--ink-3);
}
.section--dark .label{ color:rgba(255,255,255,.44); }

/* ---------- 头部 ---------- */
.hdr{
  position:fixed; top:0; left:0; right:0; z-index:60;
  transition:background .4s ease, border-color .4s ease;
  border-bottom:1px solid transparent;
}
/* 图片上的头部始终有一层极轻的压暗，保证导航可读又不压住船体 */
.hdr::before{ content:''; position:absolute; left:0; right:0; top:0; height:150%;
  background:linear-gradient(180deg, rgba(12,16,19,.62) 0%, rgba(12,16,19,.28) 55%, rgba(12,16,19,0) 100%);
  pointer-events:none; transition:opacity .4s ease; }
.hdr.is-solid::before{ opacity:0; }
.hdr__in{ position:relative; }
.hdr.is-solid{ background:rgba(12,16,19,.92); backdrop-filter:saturate(160%) blur(16px); border-bottom-color:var(--line-dark); }
.hdr__in{
  max-width:var(--maxw); margin:0 auto; padding:0 var(--gutter);
  height:84px; display:flex; align-items:center; gap:44px;
}
.hdr__logo img{ height:30px; width:auto; }
.hdr__nav{ display:flex; align-items:center; gap:34px; margin-left:auto; }
.hdr__nav a{
  font-size:13.5px; font-weight:400; color:rgba(255,255,255,.72);
  padding:6px 0; transition:color .25s ease;
}
.hdr__nav a:hover{ color:#fff; }
.hdr__lang{ display:flex; align-items:center; gap:2px; }
.hdr__lang button{
  font-family:var(--mono); font-size:10.5px; letter-spacing:.14em;
  background:none; border:0; cursor:pointer; padding:6px 9px;
  color:rgba(255,255,255,.42); transition:color .25s ease;
}
.hdr__lang button:hover{ color:rgba(255,255,255,.8); }
.hdr__lang button[aria-current="true"]{ color:#fff; }
.hdr__cta{
  font-family:var(--mono); font-size:10.5px; letter-spacing:.16em; text-transform:uppercase;
  color:#fff; border-bottom:1px solid rgba(255,255,255,.32);
  padding-bottom:5px; transition:border-color .25s ease;
}
.hdr__cta:hover{ border-color:#fff; }

/* ---------- 按钮 ---------- */
.btn{
  display:inline-flex; align-items:center; gap:16px;
  font-family:var(--mono); font-size:11px; font-weight:500;
  letter-spacing:.16em; text-transform:uppercase;
  color:var(--ink); border-bottom:1px solid var(--line-2);
  padding-bottom:12px; transition:border-color .3s ease, gap .3s ease;
}
.btn:hover{ border-color:var(--ink); gap:22px; }
.btn--light{ color:#fff; border-bottom-color:rgba(255,255,255,.3); }
.btn--light:hover{ border-bottom-color:#fff; }
.btn svg{ flex:none; }

/* ---------- 图片 ---------- */
.figure{ position:relative; overflow:hidden; background:var(--wash); }
.figure img{ width:100%; height:100%; object-fit:cover; transition:transform 1.4s cubic-bezier(.16,.84,.28,1); }
a:hover > .figure img, .figure:hover img{ transform:scale(1.04); }
.figure--16x9{ aspect-ratio:16/9; }
.figure--4x3{ aspect-ratio:4/3; }
.figure--3x4{ aspect-ratio:3/4; }
.figure--21x9{ aspect-ratio:21/9; }

/* ---------- 章节标题块 ---------- */
.shead{ max-width:60ch; margin-bottom:104px; }
.shead .lede{ margin-top:28px; }
.shead .h-1 + .lede,
.shead .h-2 + .lede{ margin-top:28px; }

/* ---------- 通用 ---------- */
.grid{ display:grid; gap:var(--gutter); }
.rule{ height:1px; background:var(--line); border:0; margin:0; }
.section--dark .rule{ background:var(--line-dark); }

@media (max-width:1080px){
  :root{ --gutter:32px; --pad:112px; }
  .hdr__nav{ display:none; }
  .hdr__in{ height:72px; }
}
@media (max-width:720px){
  :root{ --gutter:22px; --pad:84px; }
  body{ font-size:15.5px; }
  .lede{ font-size:17.5px; }
  .eyebrow{ margin-bottom:26px; }
}
@media (max-width:1080px){ .shead{ margin-bottom:64px; } }