/* =========================================================
   MJWN — 极简黑白
   无外部依赖、无网络字体，首屏只有一个 HTML + 一个 CSS
   ========================================================= */

:root {
  --bg: #ffffff;
  --fg: #0a0a0a;
  --muted: #6e6e6e;
  --line: rgba(10, 10, 10, 0.14);
  --line-strong: rgba(10, 10, 10, 0.28);

  --max: 1120px;
  --pad: clamp(20px, 5vw, 64px);
  --nav-h: 68px;

  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, "Helvetica Neue",
    "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  --font-mono: "SF Mono", ui-monospace, "Cascadia Mono", Menlo, Consolas,
    "Liberation Mono", monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0a0a0a;
    --fg: #f2f2f2;
    --muted: #9a9a9a;
    --line: rgba(242, 242, 242, 0.16);
    --line-strong: rgba(242, 242, 242, 0.32);
  }
}

/* ---------- 基础 ---------- */

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-h);
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, p, dl, dd, ul { margin: 0; }
ul { padding: 0; list-style: none; }
a { color: inherit; text-decoration: none; }
img, svg { display: block; max-width: 100%; }

::selection {
  background: var(--fg);
  color: var(--bg);
}

.wrap {
  max-width: var(--max);
  margin: 0 auto;
  padding-inline: var(--pad);
}

.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--fg);
  color: var(--bg);
  padding: 12px 18px;
  z-index: 200;
  font-size: 14px;
}
.skip:focus { left: 12px; top: 12px; }

/* ---------- 导航 ---------- */

.nav {
  position: fixed;
  inset: 0 0 auto 0;
  height: var(--nav-h);
  z-index: 100;
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  backdrop-filter: saturate(180%) blur(14px);
  -webkit-backdrop-filter: saturate(180%) blur(14px);
  border-bottom: 1px solid transparent;
  transition: border-color 0.3s var(--ease);
}
.nav.is-scrolled { border-bottom-color: var(--line); }

.nav__inner {
  max-width: var(--max);
  margin: 0 auto;
  padding-inline: var(--pad);
  height: 100%;
  display: flex;
  align-items: center;
  gap: 32px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 600;
  letter-spacing: 0.14em;
  font-size: 13px;
}
.brand__mark {
  width: 12px;
  height: 12px;
  background: var(--fg);
  display: block;
  transition: transform 0.4s var(--ease);
}
.brand:hover .brand__mark { transform: rotate(45deg); }

.nav__links {
  display: flex;
  gap: 28px;
  margin-left: auto;
  font-size: 14px;
}
.nav__links a {
  position: relative;
  color: var(--muted);
  transition: color 0.25s var(--ease);
}
.nav__links a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -4px;
  width: 100%;
  height: 1px;
  background: currentColor;
  transform: scaleX(0);
  transform-origin: right;
  transition: transform 0.35s var(--ease);
}
.nav__links a:hover { color: var(--fg); }
.nav__links a:hover::after { transform: scaleX(1); transform-origin: left; }

.nav__cta {
  font-size: 13px;
  padding: 9px 18px;
  border: 1px solid var(--line-strong);
  transition: background 0.25s var(--ease), color 0.25s var(--ease),
    border-color 0.25s var(--ease);
  white-space: nowrap;
}
.nav__cta:hover {
  background: var(--fg);
  color: var(--bg);
  border-color: var(--fg);
}

/* ---------- 首屏 ---------- */

.hero {
  padding-top: calc(var(--nav-h) + clamp(56px, 12vh, 140px));
  padding-bottom: clamp(56px, 10vh, 120px);
}

.eyebrow {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: clamp(24px, 5vh, 48px);
}

.hero__title {
  font-size: clamp(52px, 11.5vw, 148px);
  line-height: 0.94;
  letter-spacing: -0.035em;
  font-weight: 500;
  margin-bottom: clamp(40px, 7vh, 72px);
}
.hero__title .dot { font-weight: 300; }

.hero__foot {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  justify-content: space-between;
  gap: 32px;
  padding-top: 28px;
  border-top: 1px solid var(--line);
}

.hero__lead {
  font-size: clamp(15px, 1.3vw, 17px);
  color: var(--muted);
  line-height: 1.75;
  max-width: 46ch;
  text-wrap: pretty;
}

.hero__actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

/* ---------- 按钮 ---------- */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 48px;
  padding: 0 26px;
  font-size: 14px;
  letter-spacing: 0.01em;
  border: 1px solid var(--fg);
  transition: background 0.25s var(--ease), color 0.25s var(--ease),
    transform 0.25s var(--ease);
}
.btn--solid {
  background: var(--fg);
  color: var(--bg);
}
.btn--solid:hover { transform: translateY(-2px); }

.btn--ghost {
  background: transparent;
  color: var(--fg);
  border-color: var(--line-strong);
}
.btn--ghost:hover {
  border-color: var(--fg);
  transform: translateY(-2px);
}

/* ---------- 通用区块 ---------- */

.section {
  padding-block: clamp(72px, 11vw, 148px);
  border-top: 1px solid var(--line);
}

.section__head {
  display: flex;
  align-items: baseline;
  gap: 18px;
  margin-bottom: clamp(36px, 6vw, 64px);
}

.idx {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--muted);
  letter-spacing: 0.1em;
}

.section__title {
  font-size: clamp(26px, 3.4vw, 40px);
  font-weight: 500;
  letter-spacing: -0.02em;
}

/* ---------- 关于 ---------- */

.about {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: clamp(32px, 6vw, 96px);
}

.about__lead {
  font-size: clamp(22px, 2.6vw, 32px);
  line-height: 1.4;
  letter-spacing: -0.02em;
  font-weight: 400;
}

.about__body p {
  color: var(--muted);
  font-size: 15px;
  line-height: 1.85;
  max-width: 52ch;
  text-wrap: pretty;
}
.about__body p + p { margin-top: 18px; }

.stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  margin-top: clamp(48px, 8vw, 88px);
  border-top: 1px solid var(--line);
}

.stat {
  padding: 28px 24px 28px 0;
  border-right: 1px solid var(--line);
}
.stat:last-child { border-right: 0; }
.stat + .stat { padding-left: 24px; }

.stat dt {
  font-size: 12px;
  color: var(--muted);
  letter-spacing: 0.06em;
  margin-bottom: 10px;
}
.stat dd {
  font-size: clamp(28px, 3.4vw, 42px);
  font-weight: 400;
  letter-spacing: -0.02em;
  line-height: 1;
}
.stat dd span {
  font-size: 13px;
  color: var(--muted);
  margin-left: 4px;
  letter-spacing: 0;
}

/* ---------- 能力行 ---------- */

.rows { border-top: 1px solid var(--line); }

.row {
  position: relative;
  display: grid;
  grid-template-columns: 64px minmax(140px, 0.9fr) 1.7fr 32px;
  align-items: start;
  gap: clamp(16px, 3vw, 40px);
  padding: 30px 8px;
  border-bottom: 1px solid var(--line);
  transition: background 0.35s var(--ease), color 0.35s var(--ease),
    padding 0.35s var(--ease);
}

.row__idx {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--muted);
  padding-top: 6px;
  transition: color 0.35s var(--ease);
}

.row__title {
  font-size: clamp(19px, 2vw, 24px);
  font-weight: 500;
  letter-spacing: -0.01em;
  padding-top: 2px;
}

.row__desc {
  font-size: 14px;
  line-height: 1.75;
  color: var(--muted);
  max-width: 46ch;
  transition: color 0.35s var(--ease);
}

.row__arrow {
  justify-self: end;
  font-size: 18px;
  color: var(--muted);
  opacity: 0;
  transform: translate(-6px, 6px);
  transition: opacity 0.35s var(--ease), transform 0.35s var(--ease),
    color 0.35s var(--ease);
}

/* 悬停反相：黑白站点的标志性交互 */
@media (hover: hover) {
  .row:hover {
    background: var(--fg);
    color: var(--bg);
    padding-inline: 20px;
  }
  .row:hover .row__idx,
  .row:hover .row__desc,
  .row:hover .row__arrow { color: var(--bg); }
  .row:hover .row__arrow {
    opacity: 1;
    transform: translate(0, 0);
  }
}

/* ---------- 团队 ---------- */

.team__intro {
  color: var(--muted);
  font-size: 15px;
  max-width: 54ch;
  margin-bottom: clamp(32px, 5vw, 56px);
  text-wrap: pretty;
}

.team {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1px;
  background: var(--line);
  border-block: 1px solid var(--line);
}

.member {
  background: var(--bg);
  padding: clamp(24px, 3vw, 36px) clamp(20px, 2.5vw, 28px);
  display: flex;
  flex-direction: column;
  gap: 18px;
  transition: background 0.35s var(--ease);
}

.member__initials {
  width: 44px;
  height: 44px;
  display: grid;
  place-items: center;
  border: 1px solid var(--line-strong);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--muted);
  transition: background 0.35s var(--ease), color 0.35s var(--ease),
    border-color 0.35s var(--ease);
}

.member h3 {
  font-size: 18px;
  font-weight: 500;
  letter-spacing: -0.01em;
}

.member__role {
  font-size: 12px;
  color: var(--muted);
  letter-spacing: 0.04em;
  margin-top: 6px;
}

.member__note {
  font-size: 13px;
  color: var(--muted);
  line-height: 1.75;
  margin-top: 14px;
}

@media (hover: hover) {
  .member:hover { background: var(--fg); }
  .member:hover h3,
  .member:hover .member__note { color: var(--bg); }
  .member:hover .member__role { color: var(--bg); opacity: 0.6; }
  .member:hover .member__initials {
    background: var(--bg);
    color: var(--fg);
    border-color: var(--bg);
  }
}

/* ---------- 联系 ---------- */

.section--contact { padding-bottom: clamp(72px, 10vw, 140px); }

.contact__lead {
  color: var(--muted);
  font-size: 15px;
  margin-bottom: 28px;
}

.contact__mail {
  display: inline-block;
  font-size: clamp(26px, 5.2vw, 64px);
  line-height: 1.15;
  letter-spacing: -0.03em;
  font-weight: 400;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--line-strong);
  transition: border-color 0.3s var(--ease), letter-spacing 0.4s var(--ease);
  word-break: break-word;
}
.contact__mail:hover {
  border-bottom-color: var(--fg);
  letter-spacing: -0.01em;
}

.contact__meta {
  display: flex;
  gap: clamp(40px, 8vw, 96px);
  margin-top: clamp(40px, 6vw, 64px);
  padding-top: 28px;
  border-top: 1px solid var(--line);
  font-size: 14px;
}

.contact__meta .label {
  display: block;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 8px;
}

/* ---------- 页脚 ---------- */

.footer {
  border-top: 1px solid var(--line);
  padding-block: 32px;
}

.footer__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  flex-wrap: wrap;
  font-size: 13px;
  color: var(--muted);
}

.footer__brand {
  font-weight: 600;
  letter-spacing: 0.14em;
  font-size: 12px;
  color: var(--fg);
}

.footer__top { transition: color 0.25s var(--ease); }
.footer__top:hover { color: var(--fg); }

/* ---------- 入场动画 ---------- */

/* 初始隐藏只作用于 .js（见 index.html 头部内联脚本），
   脚本被禁用或加载失败时内容直接可见 */
.js .reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 0.75s var(--ease), transform 0.75s var(--ease);
}
.js .reveal.is-in {
  opacity: 1;
  transform: none;
}

/* ---------- 响应式 ---------- */

@media (max-width: 900px) {
  .about { grid-template-columns: 1fr; }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .stat:nth-child(2) { border-right: 0; }
  .stat:nth-child(3),
  .stat:nth-child(4) { border-top: 1px solid var(--line); }
  .team { grid-template-columns: 1fr; }

  .row {
    grid-template-columns: 40px 1fr;
    gap: 8px 16px;
    padding: 24px 0;
  }
  .row__idx { grid-row: span 2; }
  .row__desc { grid-column: 2; }
  .row__arrow { display: none; }
  .row:hover { padding-inline: 0; }
}

@media (max-width: 640px) {
  :root { --nav-h: 60px; }

  .nav__links { display: none; }
  .nav__cta { margin-left: auto; }

  .hero__foot { flex-direction: column; align-items: flex-start; }
  .hero__actions { width: 100%; }
  .btn { flex: 1; }

  .stats { grid-template-columns: 1fr 1fr; }
  .stat { padding: 22px 16px 22px 0; }
  .stat + .stat { padding-left: 16px; }

  .contact__meta { flex-direction: column; gap: 24px; }
}

/* ---------- 无障碍：尊重「减少动态效果」 ---------- */

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
  .reveal,
  .js .reveal { opacity: 1; transform: none; }
}

/* ---------- 打印 ---------- */

@media print {
  .nav, .footer__top, .hero__actions { display: none; }
  body { color: #000; background: #fff; }
  .js .reveal { opacity: 1; transform: none; }
}