/* ═══════════════════════════════════════════════════════════════
   北京民智文化发展战略研究院 · D&C THINK — v4 "Plain"
   Institutional minimal: white, hairlines, one red rule, no motion
   ═══════════════════════════════════════════════════════════════ */

:root {
  --ink: #1c2733;
  --ink-strong: #0e1721;
  --paper: #ffffff;
  --paper-gray: #f6f5f1;
  --red: #a6362b;
  --gray: #5c6874;
  --line: #d9d9d4;
  --line-dark: rgba(255, 255, 255, 0.16);

  --serif-zh: "Noto Serif SC", "Songti SC", "SimSun", serif;
  --serif-en: "Playfair Display", Georgia, serif;
  --sans: "Inter", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;

  --container: 1080px;
  --container-wide: 1240px;
}

/* ── Reset ─────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: var(--sans);
  background: var(--paper);
  color: var(--ink);
  line-height: 1.85;
  font-size: 15.5px;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

::selection { background: var(--red); color: #fff; }
::-webkit-scrollbar { width: 10px; }
::-webkit-scrollbar-track { background: var(--paper-gray); }
::-webkit-scrollbar-thumb { background: #b9b9b2; }
:focus-visible { outline: 2px solid var(--red); outline-offset: 2px; }

img, svg { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font: inherit; cursor: pointer; background: none; border: 0; color: inherit; }
ul { list-style: none; }

.container { max-width: var(--container); margin: 0 auto; padding: 0 clamp(18px, 3.5vw, 40px); }
.container-wide { max-width: var(--container-wide); margin: 0 auto; padding: 0 clamp(18px, 3.5vw, 40px); }

/* ═══════════════ HEADER ═══════════════ */
.site-header {
  position: sticky; top: 0; z-index: 100;
  background: var(--paper);
  border-top: 3px solid var(--red);
  border-bottom: 1px solid var(--line);
}
.header-inner {
  display: flex; align-items: center; justify-content: space-between;
  gap: clamp(12px, 2vw, 24px);
  height: 78px;
}

.brand { display: flex; align-items: center; gap: 14px; min-width: 0; flex: none; }
.brand-logo { height: 44px; width: auto; flex: none; }
.brand-text { display: grid; gap: 1px; padding-left: 14px; border-left: 1px solid var(--line); }
.brand-zh { font-family: var(--serif-zh); font-size: 1.1rem; font-weight: 700; letter-spacing: 0.1em; white-space: nowrap; }
body.lang-en .brand-zh { font-family: var(--serif-en); letter-spacing: 0.02em; }
.brand-sub { font-size: 0.62rem; letter-spacing: 0.12em; color: var(--gray); white-space: nowrap; }
body.lang-en .brand-sub { font-size: 0.6rem; letter-spacing: 0.04em; }

.main-nav { display: flex; align-items: center; gap: clamp(10px, 1.6vw, 22px); }
.nav-link {
  font-size: 0.88rem; font-weight: 500; letter-spacing: 0.04em;
  color: var(--ink); padding: 6px 2px;
  border-bottom: 2px solid transparent;
}
.nav-link:hover { color: var(--red); border-bottom-color: var(--red); }

.header-actions { display: flex; align-items: center; gap: 14px; flex: none; }
.lang-switch { display: flex; border: 1px solid var(--line); }
.lang-btn {
  font-size: 0.74rem; font-weight: 600; padding: 4px 12px;
  color: var(--gray);
}
.lang-btn + .lang-btn { border-left: 1px solid var(--line); }
.lang-btn.active { background: var(--red); color: #fff; }

.menu-toggle {
  display: none; flex-direction: column; justify-content: center; gap: 6px;
  width: 42px; height: 42px; padding: 10px;
}
.menu-toggle span { display: block; height: 1.5px; width: 100%; background: var(--ink); }
.menu-toggle.open span:nth-child(1) { transform: translateY(3.75px) rotate(45deg); }
.menu-toggle.open span:nth-child(2) { transform: translateY(-3.75px) rotate(-45deg); }

/* ═══════════════ HERO ═══════════════ */
.hero { padding: clamp(64px, 9vw, 110px) 0 0; }
.hero-eyebrow {
  font-size: 0.78rem; letter-spacing: 0.22em; color: var(--gray);
  margin-bottom: 22px;
}
.hero-title {
  font-family: var(--serif-zh);
  font-size: clamp(2.1rem, 4.6vw, 3.3rem);
  font-weight: 700; letter-spacing: 0.1em; line-height: 1.3;
  margin-bottom: 12px;
}
body.lang-en .hero-title { font-family: var(--serif-en); letter-spacing: 0; }
.hero-sub {
  font-family: var(--serif-zh);
  font-size: clamp(1.05rem, 1.6vw, 1.3rem);
  font-weight: 600; letter-spacing: 0.14em;
  color: var(--ink-strong); margin-bottom: 26px;
}
body.lang-en .hero-sub { font-family: var(--serif-en); letter-spacing: 0; }
.hero-desc { max-width: 720px; color: #3d4a56; margin-bottom: 34px; }

.hero-actions { display: flex; flex-wrap: wrap; gap: 14px; margin-bottom: clamp(48px, 6vw, 72px); }

.btn {
  display: inline-flex; align-items: center; justify-content: center;
  padding: 11px 28px;
  font-size: 0.9rem; font-weight: 500; letter-spacing: 0.06em;
  border: 1px solid var(--ink);
}
.btn-solid { background: var(--ink); color: var(--paper); }
.btn-solid:hover { background: var(--red); border-color: var(--red); }
.btn-outline { background: transparent; color: var(--ink); }
.btn-outline:hover { border-color: var(--red); color: var(--red); }

/* facts strip */
.hero-facts { border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); background: var(--paper-gray); }
.hero-facts-inner { display: grid; grid-template-columns: repeat(4, 1fr); }
.fact {
  display: flex; flex-direction: column; align-items: center; gap: 2px;
  padding: 22px 10px; text-align: center;
  border-left: 1px solid var(--line);
}
.fact:first-child { border-left: 0; }
.fact b { font-family: var(--serif-en); font-size: 1.7rem; font-weight: 600; color: var(--ink-strong); }
body.lang-zh .fact b { font-family: var(--serif-zh); }
.fact span { font-size: 0.78rem; letter-spacing: 0.1em; color: var(--gray); }

/* ═══════════════ SECTIONS ═══════════════ */
.section { padding: clamp(56px, 7vw, 88px) 0; }
.section-gray { background: var(--paper-gray); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }

.section-head { margin-bottom: clamp(30px, 4vw, 44px); }
.section-title {
  display: flex; align-items: center; gap: 16px;
  font-family: var(--serif-zh);
  font-size: clamp(1.4rem, 2.4vw, 1.75rem);
  font-weight: 700; letter-spacing: 0.12em;
  color: var(--ink-strong);
}
body.lang-en .section-title { font-family: var(--serif-en); letter-spacing: 0; }
.section-title::before {
  content: ""; width: 5px; height: 1.15em; background: var(--red); flex: none;
}

/* ═══════════════ ABOUT ═══════════════ */
.about-grid { display: grid; grid-template-columns: 1.7fr 1fr; gap: clamp(32px, 5vw, 64px); align-items: start; }
.about-text p { margin-bottom: 16px; color: #333f4b; }

.about-goals {
  display: flex; align-items: baseline; gap: 18px; flex-wrap: wrap;
  margin-top: 26px; padding: 16px 20px;
  border: 1px solid var(--line); background: var(--paper-gray);
}
.ag-label { font-size: 0.8rem; font-weight: 700; letter-spacing: 0.2em; color: var(--red); }
.ag-items { font-family: var(--serif-zh); font-weight: 600; letter-spacing: 0.08em; }

.about-info { border: 1px solid var(--line); }
.ai-title {
  font-size: 0.82rem; font-weight: 700; letter-spacing: 0.24em;
  color: var(--paper); background: var(--ink-strong);
  padding: 10px 18px;
}
.info-list { display: grid; }
.info-row {
  display: grid; grid-template-columns: 76px 1fr; gap: 14px;
  padding: 12px 18px;
  border-bottom: 1px solid var(--line);
  font-size: 0.88rem;
}
.info-row:last-child { border-bottom: 0; }
.info-row dt { color: var(--gray); white-space: nowrap; }
.info-row dd { color: var(--ink); }

/* ═══════════════ PLAIN GRID (research & business) ═══════════════ */
.plain-grid { display: grid; grid-template-columns: 1fr 1fr; border-top: 1px solid var(--line); border-left: 1px solid var(--line); background: var(--paper); }
.plain-item {
  display: flex; flex-direction: column;
  padding: 24px 26px;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.plain-item > div { min-width: 0; }
.plain-grid-numbered .plain-item { flex-direction: row; }
.plain-item h3 {
  font-family: var(--serif-zh);
  font-size: 1.05rem; font-weight: 700; letter-spacing: 0.06em;
  margin-bottom: 8px; color: var(--ink-strong);
  flex: none;
}
body.lang-en .plain-item h3 { font-family: var(--serif-en); }
.plain-item p { font-size: 0.88rem; color: #4a5560; }
.plain-grid-numbered .pn {
  font-family: var(--serif-en); font-size: 0.95rem; font-weight: 600;
  color: var(--red); margin-right: 18px; flex: none; padding-top: 2px;
}

/* ═══════════════ PUBLICATIONS ═══════════════ */
.pub-columns { display: grid; grid-template-columns: 1fr 1fr; gap: clamp(28px, 4vw, 56px); align-items: start; }
.pg-title {
  font-size: 0.85rem; font-weight: 700; letter-spacing: 0.2em;
  color: var(--ink-strong);
  padding: 10px 0;
  border-bottom: 2px solid var(--ink-strong);
  margin-bottom: 4px;
}
.pub-group .pg-title + .doc-list,
.pub-group .pg-title + .doc-inline,
.pub-group .pg-title + .doc-text { margin-top: 4px; }
.pub-group .pg-title:not(:first-child) { margin-top: 30px; }

.doc-list { display: grid; }
.doc-list li {
  padding: 11px 2px;
  border-bottom: 1px solid var(--line);
  font-size: 0.92rem;
  padding-left: 16px; position: relative;
}
.doc-list li::before {
  content: ""; position: absolute; left: 0;
  top: calc(11px + 0.925em - 0.75px); /* padding-top + half line-height - half dash */
  width: 6px; height: 1.5px; background: var(--red);
}
.doc-inline { font-family: var(--serif-zh); font-size: 0.95rem; padding: 12px 2px; border-bottom: 1px solid var(--line); }
.doc-text { font-size: 0.9rem; color: #4a5560; padding: 10px 2px; }

/* ═══════════════ TEAM ═══════════════ */
.team-grid { display: grid; grid-template-columns: 1fr 1fr; gap: clamp(28px, 4vw, 56px); align-items: start; }
.tm-col-title {
  font-size: 0.85rem; font-weight: 700; letter-spacing: 0.2em;
  color: var(--ink-strong);
  padding: 10px 0;
  border-bottom: 2px solid var(--ink-strong);
  margin-bottom: 4px;
}
.team-list { display: grid; }
.team-list li {
  display: grid; grid-template-columns: 110px 1fr; gap: 16px;
  padding: 12px 2px;
  border-bottom: 1px solid var(--line);
  font-size: 0.9rem;
}
.tm-name { font-family: var(--serif-zh); font-weight: 700; letter-spacing: 0.04em; color: var(--ink-strong); }
body.lang-en .tm-name { font-family: var(--serif-en); }
.tm-role { color: #4a5560; }

/* ═══════════════ EVENTS TABLE ═══════════════ */
.event-table { border: 1px solid var(--line); background: var(--paper); }
.et-row {
  display: grid; grid-template-columns: 110px 1.1fr 1.6fr; gap: 20px;
  padding: 14px 20px;
  border-bottom: 1px solid var(--line);
  font-size: 0.9rem;
}
.et-row:last-child { border-bottom: 0; }
.et-head {
  background: var(--ink-strong); color: var(--paper);
  font-size: 0.8rem; font-weight: 600; letter-spacing: 0.14em;
  padding: 9px 20px;
}
.et-type { color: var(--red); font-weight: 600; }
.et-name { font-family: var(--serif-zh); font-weight: 600; color: var(--ink-strong); }
body.lang-en .et-name { font-family: var(--serif-en); }
.et-note { color: #4a5560; }

/* ═══════════════ CONTACT ═══════════════ */
.contact-table { border: 1px solid var(--line); background: var(--paper); }
.ct-row {
  display: grid; grid-template-columns: 130px 1fr; gap: 20px;
  padding: 15px 22px;
  border-bottom: 1px solid var(--line);
  font-size: 0.94rem;
}
.ct-row:last-child { border-bottom: 0; }
.ct-label { font-weight: 700; letter-spacing: 0.1em; color: var(--ink-strong); }
.ct-value { color: #333f4b; }
.ct-value a { color: var(--red); border-bottom: 1px solid rgba(166, 54, 43, 0.4); }
.ct-value a:hover { border-bottom-color: var(--red); }
.contact-cta { margin-top: 24px; }

/* ═══════════════ FOOTER ═══════════════ */
.site-footer { background: var(--ink-strong); color: rgba(255, 255, 255, 0.66); }
.footer-top {
  display: flex; align-items: center; justify-content: space-between; gap: 30px;
  flex-wrap: wrap;
  padding: 34px 0 26px;
  border-bottom: 1px solid var(--line-dark);
}
.footer-logo { height: 42px; width: auto; }
.footer-nav { display: flex; flex-wrap: wrap; gap: clamp(12px, 2vw, 26px); }
.footer-nav a { font-size: 0.86rem; color: rgba(255, 255, 255, 0.62); }
.footer-nav a:hover { color: #fff; }
.footer-bottom {
  display: flex; justify-content: space-between; align-items: center; gap: 14px; flex-wrap: wrap;
  padding: 20px 0 26px;
  font-size: 0.78rem; color: rgba(255, 255, 255, 0.4);
}
.footer-icp a { transition: color 0.2s; }
.footer-icp a:hover { color: rgba(255, 255, 255, 0.7); }

/* ═══════════════ BACK TO TOP ═══════════════ */
.back-top {
  position: fixed; right: 22px; bottom: 22px; z-index: 90;
  width: 44px; height: 44px;
  background: var(--paper); color: var(--ink);
  border: 1px solid var(--line);
  display: grid; place-items: center;
  visibility: hidden; opacity: 0;
}
.back-top.show { visibility: visible; opacity: 1; }
.back-top:hover { border-color: var(--red); color: var(--red); }
.back-top svg { width: 18px; height: 18px; }

/* ═══════════════ RESPONSIVE ═══════════════
   Header balance strategy: give every width band enough room —
   long EN subtitle hides first (1260), nav collapses to menu next
   (1120), ZH subtitle hides at 760, then tiered shrinking for
   narrow phones so brand and lang-switch never collide. */

@media (max-width: 1260px) {
  body.lang-en .brand-sub { display: none; }
}

@media (max-width: 1120px) {
  .main-nav {
    position: fixed; inset: 0;
    flex-direction: column; justify-content: center;
    background: var(--paper);
    gap: 4px;
    visibility: hidden; opacity: 0;
    z-index: -1;
  }
  .main-nav.open { visibility: visible; opacity: 1; z-index: 95; }
  .nav-link { font-family: var(--serif-zh); font-size: 1.25rem; font-weight: 600; padding: 10px 0; border: 0; }
  .menu-toggle { display: flex; z-index: 96; position: relative; }
}

@media (max-width: 980px) {
  .about-grid { grid-template-columns: 1fr; }
  .pub-columns { grid-template-columns: 1fr; }
  .team-grid { grid-template-columns: 1fr; }
  .hero-facts-inner { grid-template-columns: repeat(2, 1fr); }
  .fact:nth-child(3) { border-left: 0; }
  .fact:nth-child(-n+2) { border-bottom: 1px solid var(--line); }
}

@media (max-width: 760px) {
  .brand-sub { display: none; }
  .brand-text { border-left: 0; padding-left: 0; }
}

@media (max-width: 640px) {
  body { font-size: 15px; }
  .brand { gap: 10px; }
  .brand-logo { height: 38px; }
  .hero-actions .btn { width: 100%; }
  .plain-grid { grid-template-columns: 1fr; }
  .et-row { grid-template-columns: 1fr; gap: 6px; }
  .et-head { display: none; }
  .ct-row { grid-template-columns: 1fr; gap: 6px; }
  .team-list li { grid-template-columns: 92px 1fr; }
  .footer-bottom { flex-direction: column; align-items: flex-start; }
}

@media (max-width: 480px) {
  .header-inner { gap: 10px; }
  .header-actions { gap: 10px; }
  .brand { gap: 8px; }
  .brand-logo { height: 34px; }
  .brand-zh { font-size: 1rem; letter-spacing: 0.05em; }
  .lang-btn { padding: 4px 10px; }
  .menu-toggle { width: 40px; height: 40px; }
}

@media (max-width: 380px) {
  .brand-logo { height: 31px; }
  .brand-zh { font-size: 0.92rem; letter-spacing: 0.02em; }
  .lang-btn { padding: 4px 8px; font-size: 0.7rem; }
  .menu-toggle { width: 36px; height: 36px; padding: 8px; }
}