/* ==========================================================================
   ACI Institute, design system and shell
   Single source of truth for color, type, and the shared header and footer.
   Values fixed in the design brief, Sections 3.1 and 3.2.
   ========================================================================== */

:root {
  color-scheme: light;

  /* Foundation */
  --parchment: #F3EAD3;
  --parchment-deep: #EADCBF;
  --ink: #2A2420;
  --ink-soft: #5B5147;
  --line: #D8C9A6;

  /* Brand (Manus, the Design Object center of Figure 5.3) */
  --manus: #9A3412;
  --manus-bright: #B4512A;

  /* The four creative capabilities (fixed, from Figure 5.3) */
  --ee-blue: #3E6EA5;   /* Extended Engagement  / World Models */
  --aa-olive: #6E7B3D;  /* Aesthetic Awareness  / Large Language Models */
  --ac-purple: #5E4B8B; /* Adaptive Coherence   / Causal Models */
  --ei-orange: #C8721F; /* Expressive Influence / Diffusion Models */

  /* Type families */
  --font-display: "Fraunces", Georgia, "Times New Roman", serif;
  --font-body: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, "SF Mono", Menlo, monospace;
  --font-cjk: "PingFang SC", "Microsoft YaHei", "Noto Sans SC", sans-serif;

  /* Type scale (~1.25 ratio) */
  --fs-display: clamp(2.5rem, 5vw, 4rem);
  --fs-h1: clamp(2rem, 3.5vw, 2.5rem);
  --fs-h2: 1.75rem;
  --fs-h3: 1.375rem;
  --fs-body: 1.125rem;
  --fs-small: 0.9375rem;

  /* Layout */
  --maxw: 1200px;
  --measure: 68ch;
  --radius: 10px;
  --header-h: 68px;
}

/* Chinese pages swap to a CJK stack so CN reads as designed, not defaulted. */
html[lang^="zh"] {
  --font-body: "PingFang SC", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  --font-display: "Songti SC", "STSong", "Noto Serif SC", "PingFang SC", serif;
}

/* --- Reset and base ------------------------------------------------------ */

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--parchment);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
h1, h2, h3 { font-family: var(--font-display); line-height: 1.15; font-weight: 600; }
a { color: var(--manus); }
img { max-width: 100%; height: auto; }

.wrap { max-width: var(--maxw); margin-inline: auto; padding-inline: 1.5rem; }

.skip-link {
  position: absolute; left: 0.5rem; top: -3rem;
  background: var(--manus); color: #fff; padding: 0.5rem 0.9rem;
  border-radius: 8px; text-decoration: none; z-index: 100;
  transition: top 0.15s ease;
}
.skip-link:focus { top: 0.5rem; }

:where(a, button, [tabindex]):focus-visible {
  outline: 2px solid var(--manus);
  outline-offset: 2px;
  border-radius: 4px;
}

/* --- Buttons ------------------------------------------------------------- */

.btn {
  display: inline-flex; align-items: center; justify-content: center;
  padding: 0.55rem 1.05rem; border-radius: 999px;
  font-family: var(--font-body); font-weight: 600; font-size: 0.95rem;
  text-decoration: none; border: 1px solid transparent; cursor: pointer;
  transition: background 0.15s ease, color 0.15s ease, border-color 0.15s ease;
}
.btn-primary { background: var(--manus); color: #fff; }
.btn-primary:hover { background: var(--manus-bright); }
.btn-quiet { background: transparent; color: var(--ink); border-color: var(--line); }
.btn-quiet:hover { color: var(--manus); border-color: var(--manus); }

/* --- Header -------------------------------------------------------------- */

.site-header {
  position: sticky; top: 0; z-index: 20;
  background: var(--parchment); /* fallback where color-mix is unsupported */
  background: color-mix(in srgb, var(--parchment) 88%, transparent);
  -webkit-backdrop-filter: saturate(1.1) blur(8px);
  backdrop-filter: saturate(1.1) blur(8px);
  border-bottom: 1px solid var(--line);
}
.header-inner {
  display: flex; align-items: center; gap: 1.25rem;
  min-height: var(--header-h);
}
.brand {
  display: inline-flex; align-items: center; gap: 0.5rem;
  text-decoration: none; color: var(--ink);
  font-family: var(--font-display); font-weight: 600; font-size: 1.25rem;
  white-space: nowrap;
}
.brand-mark { display: inline-flex; }
.site-nav { display: flex; gap: 1.15rem; margin-left: auto; }
.site-nav a {
  color: var(--ink-soft); text-decoration: none; font-size: 0.975rem;
}
.site-nav a:hover { color: var(--manus); }
.site-nav a[aria-current="page"] { color: var(--manus); font-weight: 600; }
.footer-col a[aria-current="page"] { color: var(--manus); }
.header-actions { display: flex; align-items: center; gap: 0.7rem; }

.lang-switch {
  display: inline-flex; border: 1px solid var(--line);
  border-radius: 999px; overflow: hidden;
}
.lang-switch button {
  border: 0; background: transparent; cursor: pointer;
  padding: 0.35rem 0.6rem; font-family: var(--font-body);
  font-size: 0.8rem; color: var(--ink-soft);
}
.lang-switch button[aria-pressed="true"] { background: var(--manus); color: #fff; }

.nav-toggle {
  display: none; margin-left: auto;
  background: transparent; border: 1px solid var(--line); border-radius: 8px;
  font-size: 1.1rem; line-height: 1; padding: 0.4rem 0.6rem;
  color: var(--ink); cursor: pointer;
}

/* --- Footer -------------------------------------------------------------- */

.site-footer {
  background: var(--parchment-deep);
  border-top: 1px solid var(--line);
  margin-top: 4rem;
}
.footer-inner {
  display: grid; grid-template-columns: 1.5fr 1fr 1fr 1.2fr; gap: 2rem;
  padding-block: 3rem 1.5rem;
}
.footer-brand .brand-name { font-family: var(--font-display); font-size: 1.15rem; font-weight: 600; }
.footer-tagline { color: var(--ink-soft); font-size: 0.95rem; max-width: 26ch; margin: 0.5rem 0 0; }
.footer-col h2 {
  font-family: var(--font-body); font-size: 0.78rem; font-weight: 600;
  text-transform: uppercase; letter-spacing: 0.08em; color: var(--ink-soft);
  margin: 0 0 0.7rem;
}
.footer-col a {
  display: block; color: var(--ink); text-decoration: none;
  padding: 0.2rem 0; font-size: 0.95rem;
}
.footer-col a:hover { color: var(--manus); }
.footer-meta {
  grid-column: 1 / -1; display: flex; align-items: center; gap: 1.25rem;
  flex-wrap: wrap; border-top: 1px solid var(--line);
  margin-top: 1rem; padding-top: 1.25rem;
}
.footer-legal { display: flex; gap: 1rem; }
.footer-legal a { color: var(--ink-soft); text-decoration: none; font-size: 0.85rem; }
.footer-legal a:hover { color: var(--manus); }
.footer-rights { margin: 0 0 0 auto; color: var(--ink-soft); font-size: 0.85rem; }

/* --- Shell preview (temporary, replaced by Home in Step 2) ---------------- */

#main { min-height: 40vh; }
.shell-preview { padding-block: 4rem 2rem; }
.eyebrow {
  text-transform: uppercase; letter-spacing: 0.1em;
  color: var(--manus); font-size: 0.8rem; font-weight: 600; margin: 0;
}
.shell-preview .display { font-size: var(--fs-display); margin: 0.5rem 0 1rem; }
.shell-preview p.lead { max-width: var(--measure); color: var(--ink-soft); }
.swatches { display: flex; gap: 0.75rem; margin-top: 2.25rem; flex-wrap: wrap; }
.swatch {
  width: 8rem; height: 4rem; border-radius: 8px; color: #fff;
  display: flex; align-items: flex-end; padding: 0.4rem 0.55rem;
  font-size: 0.72rem; font-weight: 600; line-height: 1.2;
}
.swatch.ee { background: var(--ee-blue); }
.swatch.aa { background: var(--aa-olive); }
.swatch.ac { background: var(--ac-purple); }
.swatch.ei { background: var(--ei-orange); }

/* --- Responsive ---------------------------------------------------------- */

@media (max-width: 900px) {
  .nav-toggle { display: inline-flex; order: 3; }
  .site-nav {
    order: 4; margin-left: 0; flex-basis: 100%;
    flex-direction: column; gap: 0.25rem;
    display: none; padding: 0.5rem 0 0.75rem;
  }
  body.nav-open .site-nav { display: flex; }
  .site-nav a { padding: 0.5rem 0; }
  .header-inner { flex-wrap: wrap; }
  .header-actions { margin-left: auto; }
  .footer-inner { grid-template-columns: 1fr 1fr; }
  .footer-brand { grid-column: 1 / -1; }
  .footer-rights { margin-left: 0; flex-basis: 100%; }
}

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; animation: none !important; }
}

/* --- Page sections and components ---------------------------------------- */

.section { padding-block: 3.5rem; }
.section + .section { border-top: 1px solid var(--line); }
.section-head { max-width: var(--measure); }
.section h2 { font-size: var(--fs-h2); margin: 0 0 0.75rem; }
.lead { font-size: 1.2rem; color: var(--ink-soft); }

/* Hero */
.hero { padding-block: 4.5rem 3rem; }
.hero .eyebrow { margin-bottom: 0.75rem; }
.hero h1 { font-size: var(--fs-display); max-width: 24ch; margin: 0 0 1rem; }
.hero .subhead { font-size: 1.2rem; color: var(--ink-soft); max-width: var(--measure); margin: 0; }
.cta-row { display: flex; gap: 0.75rem; flex-wrap: wrap; margin-top: 1.75rem; }

/* Capability cards */
.cap-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1rem; margin-top: 1.75rem; }
.cap-card {
  background: var(--parchment-deep); border-top: 4px solid var(--line);
  border-radius: 0 0 var(--radius) var(--radius); padding: 1.1rem 1.15rem 1.35rem;
}
.cap-card h3 { font-size: 1.15rem; margin: 0 0 0.25rem; }
.cap-card .aspect {
  font-size: 0.76rem; text-transform: uppercase; letter-spacing: 0.06em;
  color: var(--ink-soft); margin: 0 0 0.6rem;
}
.cap-card p { margin: 0; font-size: 0.98rem; }
.cap-card.ee { border-top-color: var(--ee-blue); } .cap-card.ee h3 { color: var(--ee-blue); }
.cap-card.aa { border-top-color: var(--aa-olive); } .cap-card.aa h3 { color: var(--aa-olive); }
.cap-card.ac { border-top-color: var(--ac-purple); } .cap-card.ac h3 { color: var(--ac-purple); }
.cap-card.ei { border-top-color: var(--ei-orange); } .cap-card.ei h3 { color: var(--ei-orange); }

/* Full-width bands */
.band { background: var(--parchment-deep); border-block: 1px solid var(--line); }
.band .wrap { padding-block: 3rem; }
.band.center { text-align: center; }
.band.center .subhead { margin-inline: auto; }
.band.center .cta-row { justify-content: center; }

/* Ways in */
.ways-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1rem; margin-top: 1.75rem; }
.way-card { border: 1px solid var(--line); border-radius: var(--radius); padding: 1.25rem; }
.way-card h3 { margin: 0 0 0.4rem; font-size: 1.1rem; }
.way-card p { margin: 0 0 0.9rem; color: var(--ink-soft); font-size: 0.98rem; }

/* Book teaser */
.book-teaser .eyebrow { margin: 0 0 0.4rem; }
.book-teaser h2 { margin: 0 0 0.25rem; }
.book-teaser .authors { color: var(--ink-soft); margin: 0 0 0.75rem; }

/* Prose (Mission and other reading pages) */
.prose { max-width: var(--measure); }
.prose h2 { font-size: var(--fs-h2); margin: 2.25rem 0 0.6rem; }
.prose h2:first-child { margin-top: 0; }
.prose p { margin: 0 0 1rem; }
.cap-def { margin: 1rem 0; padding-left: 1rem; border-left: 3px solid var(--line); }
.cap-def p { margin: 0; }
.cap-def b { color: var(--ink); }
.cap-def.ee { border-left-color: var(--ee-blue); } .cap-def.ee b { color: var(--ee-blue); }
.cap-def.aa { border-left-color: var(--aa-olive); } .cap-def.aa b { color: var(--aa-olive); }
.cap-def.ac { border-left-color: var(--ac-purple); } .cap-def.ac b { color: var(--ac-purple); }
.cap-def.ei { border-left-color: var(--ei-orange); } .cap-def.ei b { color: var(--ei-orange); }

/* People and author profiles */
.people-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 2rem; margin-top: 1.75rem; }
.person-card { display: flex; gap: 1.25rem; align-items: flex-start; }
.person-photo {
  width: 132px; height: 132px; border-radius: 14px; object-fit: cover;
  flex-shrink: 0; background: var(--parchment-deep);
}
.person-body { min-width: 0; }
.person-body h3 { margin: 0; font-size: 1.25rem; }
.person-role {
  margin: 0.15rem 0 0.6rem; font-size: 0.76rem; text-transform: uppercase;
  letter-spacing: 0.06em; color: var(--manus); font-weight: 600;
}
.person-bio { margin: 0 0 0.75rem; font-size: 0.98rem; }
.person-links { display: flex; flex-wrap: wrap; gap: 0.4rem 1rem; }
.person-links a { color: var(--manus); text-decoration: none; font-size: 0.92rem; font-weight: 600; }
.person-links a:hover { text-decoration: underline; }

@media (max-width: 900px) {
  .cap-grid { grid-template-columns: 1fr 1fr; }
  .ways-grid { grid-template-columns: 1fr; }
  .people-grid { grid-template-columns: 1fr; }
}
@media (max-width: 560px) {
  .cap-grid { grid-template-columns: 1fr; }
  .person-card { flex-direction: column; }
}

/* Advance praise (endorsers) */
.praise-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1rem; margin-top: 1.75rem; }
.praise-card {
  background: var(--parchment-deep); border-radius: var(--radius);
  border-top: 3px solid var(--manus); padding: 1.25rem;
}
.praise-quote { margin: 0 0 1rem; font-size: 1rem; line-height: 1.55; }
.praise-cite { display: flex; align-items: center; gap: 0.75rem; }
.praise-avatar {
  width: 44px; height: 44px; border-radius: 50%; flex-shrink: 0;
  display: inline-flex; align-items: center; justify-content: center;
  background: var(--parchment); color: var(--manus); font-weight: 600; font-size: 0.85rem;
  object-fit: cover; border: 1px solid var(--line);
}
.praise-meta { display: flex; flex-direction: column; min-width: 0; }
.praise-name { font-weight: 600; }
.praise-role { font-size: 0.85rem; color: var(--ink-soft); }
@media (max-width: 900px) { .praise-grid { grid-template-columns: 1fr; } }