/* ================================================================
   LXMUN · about_us.css
   Styles exclusive to the About Us page.
   Requires: global.css → components.css → about_us.css
   ================================================================ */
html {
  scroll-behavior: smooth;
}

/* ── Hero ── */
.au-hero {
  position: relative;
  min-height: 100svh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding-top: var(--navbar-h);
  /* Replace with actual image: url('../media/about_us_hero.jpg') */
  background:
    linear-gradient(to right, rgba(5, 20, 55, 0.75) 38%, rgba(0,0,0,0.25) 100%),
    url("../media/about_us_hero.png") center / cover no-repeat;
  overflow: hidden;
}

/* Decorative background pattern */
.au-hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    radial-gradient(circle at 20% 50%, rgba(53, 109, 207, 0.15) 0%, transparent 50%),
    radial-gradient(circle at 80% 30%, rgba(11, 92, 171, 0.12) 0%, transparent 45%);
  pointer-events: none;
}

.au-hero__overlay {
  display: none; /* placeholder for future image overlay tuning */
}

.au-hero__content {
  position: relative;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-sm);
  padding-inline: var(--container-pad);
  padding-bottom: var(--space-2xl);
}

.au-hero__eyebrow {
  font-family: var(--font-latin);
  font-size: var(--fs-xs);
  font-weight: 400;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: rgba(255, 255, 255, 0.6);
}

.au-hero__title {
  font-size: var(--fs-hero);
  font-weight: 900;
  letter-spacing: 0.18em;
  color: var(--color-text-light);
  line-height: 1.1;
}

.au-hero__subtitle {
  font-family: var(--font-latin);
  font-size: clamp(0.85rem, 1.4vw, 1.1rem);
  font-weight: 300;
  color: rgba(255, 255, 255, 0.65);
  letter-spacing: 0.08em;
}

/* ── Sub-navigation ── */
.au-subnav {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  display: flex;
  justify-content: center;
  background: rgba(11, 77, 143, 0.85); 
  backdrop-filter: blur(8px);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  overflow-x: auto;
  scrollbar-width: none;
}
.au-subnav::-webkit-scrollbar { display: none; }

.au-subnav__item {
  padding: var(--space-sm) var(--space-md);
  font-size: var(--fs-sm);
  font-weight: 600;
  color: rgba(255, 255, 255, 0.65);
  letter-spacing: 0.06em;
  white-space: nowrap;
  border-bottom: 3px solid transparent;
  transition: color var(--transition-base), border-color var(--transition-base);
}
.au-subnav__item:hover,
.au-subnav__item--active {
  color: #fff;
  border-bottom-color: var(--color-link);
}

/* Sticky subnav on scroll */
.au-subnav.is-sticky {
  position: fixed;
  top: var(--navbar-h);
  bottom: auto;
  z-index: 90;
  background: var(--color-primary-dark);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.2);
}


/* ── Section base ── */
.au-section {
  padding-block: var(--space-2xl);
}

.au-section--muted {
  background: var(--color-bg-muted);
}

.au-section--dark {
  background: var(--color-primary);
}
.au-section--dark .section-header__title {
  color: #fff;
}


/* ── Intro ── */
.au-intro {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: var(--space-2xl);
  align-items: start;
}

.au-intro__lead {
  font-size: var(--fs-md);
  font-weight: 600;
  color: var(--color-primary);
  line-height: 1.8;
  margin-bottom: var(--space-md);
  border-left: 4px solid var(--color-accent);
  padding-left: var(--space-md);
}

.au-intro__body {
  font-size: var(--fs-sm);
  color: #383838;
  line-height: 1.9;
  margin-bottom: var(--space-sm);
}

/* Stats block */
.au-intro__stats {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-sm);
  min-width: 260px;
}

.au-stat {
  background: var(--color-bg-muted);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: 4px;
  border-top: 3px solid var(--color-accent);
}

.au-stat__number {
  font-family: var(--font-latin);
  font-size: var(--fs-xl);
  font-weight: 900;
  color: var(--color-primary);
  line-height: 1;
}

.au-stat__label {
  font-size: var(--fs-xs);
  color: var(--color-text-muted);
  font-weight: 500;
  letter-spacing: 0.05em;
}


/* ── Timeline ── */
.au-timeline {
  display: flex;
  flex-direction: column;
  gap: 0;
  margin-top: var(--space-lg);
  background:
    linear-gradient(to bottom, rgba(245, 247, 250, 0.92), rgba(245, 247, 250, 0.92)),
    url('../media/logoNoBg.png') center / cover no-repeat;
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
}

.au-timeline__item {
  display: grid;
  grid-template-columns: 80px 40px 1fr;
  gap: 0 var(--space-sm);
  align-items: stretch;
  min-height: 100px;
}

.au-timeline__year {
  font-family: var(--font-latin);
  font-size: var(--fs-md);
  font-weight: 800;
  color: var(--color-accent);
  text-align: right;
  padding-top: 6px;
  letter-spacing: 0.04em;
}

.au-timeline__connector {
  display: flex;
  flex-direction: column;
  align-items: center;
  position: relative;
}

.au-timeline__dot {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--color-accent);
  border: 3px solid var(--color-bg-muted);
  flex-shrink: 0;
  margin-top: 8px;
  z-index: 1;
  transition: background var(--transition-base), transform var(--transition-base);
}

.au-timeline__connector::after {
  content: '';
  position: absolute;
  top: 22px;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 2px;
  background: linear-gradient(to bottom, var(--color-accent), rgba(53, 109, 207, 0.2));
}

.au-timeline__item:last-child .au-timeline__connector::after {
  display: none;
}

.au-timeline__item:hover .au-timeline__dot {
  background: var(--color-link);
  transform: scale(1.3);
}

.au-timeline__card {
  background: var(--color-bg);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  margin-bottom: var(--space-md);
  box-shadow: var(--shadow-card);
  transition: box-shadow var(--transition-base), transform var(--transition-base);
}
.au-timeline__item:hover .au-timeline__card {
  box-shadow: var(--shadow-raised);
  transform: translateX(4px);
}

.au-timeline__title {
  font-size: var(--fs-base);
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: var(--space-xs);
}

.au-timeline__desc {
  font-size: var(--fs-sm);
  color: var(--color-text-muted);
  line-height: 1.75;
}


/* ── Group Cards ── */
.au-structure__lead {
  font-size: var(--fs-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-lg);
}

.au-groups {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-md);
}

.au-group-card {
  background: var(--color-bg);
  border-radius: var(--radius-lg);
  padding: var(--space-lg) var(--space-md);
  box-shadow: var(--shadow-card);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  transition: box-shadow var(--transition-base), transform var(--transition-base);
  border-top: 4px solid transparent;
}
.au-group-card:hover {
  box-shadow: var(--shadow-raised);
  transform: translateY(-4px);
}
.au-group-card:nth-child(1) { border-top-color: #1a73e8; }
.au-group-card:nth-child(2) { border-top-color: #e83e1a; }
.au-group-card:nth-child(3) { border-top-color: #1ae87f; }
.au-group-card:nth-child(4) { border-top-color: #e8b81a; }

.au-group-card__icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 900;
  font-size: var(--fs-md);
  color: #fff;
}
.au-group-card__icon--en   { background: #1a73e8; }
.au-group-card__icon--cn   { background: #e83e1a; }
.au-group-card__icon--press { background: #16a05a; }
.au-group-card__icon--tech  { background: #c9950a; }

.au-group-card__title {
  font-size: var(--fs-base);
  font-weight: 700;
  color: var(--color-primary);
}

.au-group-card__desc {
  font-size: var(--fs-sm);
  color: var(--color-text-muted);
  line-height: 1.75;
  flex: 1;
}

.au-group-card__tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: auto;
}
.au-group-card__tags li {
  font-size: var(--fs-xs);
  font-weight: 600;
  color: var(--color-accent);
  background: rgba(11, 92, 171, 0.08);
  padding: 3px 10px;
  border-radius: 99px;
  letter-spacing: 0.04em;
}


/* ── Gallery ── */
.au-gallery {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: auto auto;
  gap: var(--space-sm);
}

.au-gallery__item--large {
  grid-column: 1 / 3;
  grid-row: 1 / 3;
}

.au-gallery__item {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.au-gallery__img {
  border-radius: var(--radius-md);
  overflow: hidden;
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  transition: transform var(--transition-base), box-shadow var(--transition-base);
}
.au-gallery__item--large .au-gallery__img { aspect-ratio: 4/3; }
.au-gallery__item:not(.au-gallery__item--large) .au-gallery__img { aspect-ratio: 3/2; }

.au-gallery__img:hover {
  transform: scale(1.02);
  box-shadow: var(--shadow-raised);
}

/* Placeholder colors — replace with background-image: url(...) */
.au-gallery__img--1 { background-image: url("../media/pkumun.png"); }
.au-gallery__img--2 { background-image: url("../media/delegate_debate.jpeg"); }
.au-gallery__img--3 { background-image: url("../media/dais.jpeg"); }
.au-gallery__img--4 { background-image: url("../media/zh.jpeg"); }
.au-gallery__img--5 { background-image: url("../media/mpc.jpg"); }

.au-gallery__caption {
  font-size: var(--fs-xs);
  color: rgba(255, 255, 255, 0.55);
  letter-spacing: 0.04em;
  padding-inline: 4px;
}


/* ── Join ── */
.au-join {
  background: var(--color-bg);
}

.au-join__inner {
  display: grid;
  grid-template-columns: 1fr 360px;
  gap: var(--space-2xl);
  align-items: center;
  background: var(--color-bg-muted);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  overflow: hidden;
  position: relative;
}

.au-join__inner::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  width: 4px;
  background: linear-gradient(to bottom, var(--color-accent), var(--color-link));
  border-radius: 2px 0 0 2px;
}

.au-join__title {
  font-size: var(--fs-2xl);
  font-weight: 800;
  color: var(--color-primary);
  letter-spacing: 0.1em;
  margin-bottom: var(--space-sm);
}

.au-join__desc {
  font-size: var(--fs-sm);
  color: var(--color-text-muted);
  line-height: 1.9;
  margin-bottom: var(--space-lg);
}

.au-join__actions {
  display: flex;
  gap: var(--space-sm);
  flex-wrap: wrap;
}

.au-join__img {
  width: 100%;
  aspect-ratio: 4/3;
  border-radius: var(--radius-md);
  background-color: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.12);
  background-size: cover;
  background-position: center;
  /* Placeholder display */
  /* display: flex; */
  align-items: center;
  justify-content: center;
  color: rgba(255, 255, 255, 0.2);
  font-size: var(--fs-sm);
  font-family: var(--font-latin);
  letter-spacing: 0.1em;
}


/* ── Responsive ── */

@media (max-width: 1024px) {
  .au-groups {
    grid-template-columns: repeat(2, 1fr);
  }

  .au-gallery {
    grid-template-columns: repeat(2, 1fr);
  }
  .au-gallery__item--large {
    grid-column: 1 / -1;
    grid-row: auto;
  }

  .au-join__inner {
    grid-template-columns: 1fr;
  }
  .au-join__img {
    height: 200px;
  }
}

@media (max-width: 768px) {
  .au-hero {
    min-height: 60svh;
  }

  .au-subnav__item {
    padding: var(--space-sm);
    font-size: var(--fs-xs);
  }

  .au-intro {
    grid-template-columns: 1fr;
    gap: var(--space-lg);
  }

  .au-intro__stats {
    min-width: unset;
    width: 100%;
  }

  .au-timeline__item {
    grid-template-columns: 56px 32px 1fr;
  }

  .au-timeline__year {
    font-size: var(--fs-sm);
  }

  .au-groups {
    grid-template-columns: 1fr;
  }

  .au-gallery {
    grid-template-columns: 1fr;
  }

  .au-join__inner {
    padding: var(--space-lg);
  }

  .au-join__actions {
    flex-direction: column;
  }
  .au-join__actions .btn {
    width: 100%;
    justify-content: center;
  }
}

@media (max-width: 480px) {
  .au-intro__stats {
    grid-template-columns: repeat(2, 1fr);
  }

  .au-timeline__item {
    grid-template-columns: 48px 28px 1fr;
  }
}