/* ============================================
   BRAND BOOK — Layout
   Page shell, grids, responsive structure
   ============================================ */

/* ---- Page Shell ---- */
.page {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.page__header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: var(--z-sticky);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-5) var(--page-gutter);
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid transparent;
  transition: border-color var(--duration-normal) var(--ease-default),
              background var(--duration-normal) var(--ease-default);
}

.page__header.scrolled {
  border-bottom-color: var(--border-subtle);
}

.page__brand-group {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.page__back {
  font-family: var(--font-body, system-ui, sans-serif);
  font-size: var(--text-xs);
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--duration-fast) var(--ease-default);
  white-space: nowrap;
}

.page__back:hover {
  color: var(--text-primary);
}

.page__brand-divider {
  width: 1px;
  height: 1rem;
  background: var(--border-default);
}

.page__brand {
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  letter-spacing: var(--tracking-wide);
  text-transform: uppercase;
  color: var(--text-primary);
  text-decoration: none;
  transition: opacity var(--duration-fast) var(--ease-default);
}

.page__brand:hover {
  opacity: 0.7;
}

.page__main {
  flex: 1;
  padding-top: calc(var(--space-20) + var(--space-8));
}

.page__footer {
  border-top: 1px solid var(--border-default);
  margin-top: var(--section-gap);
}

/* ---- Content Containers ---- */
.container {
  width: 100%;
  max-width: var(--content-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--page-gutter);
  padding-right: var(--page-gutter);
}

.container--narrow {
  max-width: var(--content-narrow);
}

.container--full {
  max-width: none;
}

/* ---- Section ---- */
.section {
  padding-bottom: var(--section-gap);
}

.section__header {
  margin-bottom: var(--space-12);
}

.section__header .overline {
  margin-bottom: var(--space-4);
}

.section__header h2 {
  margin-bottom: var(--space-4);
}

.section__header .lead {
  margin-top: var(--space-2);
}

/* ---- Page Hero ---- */
.page-hero {
  padding-bottom: var(--section-gap);
}

.page-hero .display {
  margin-bottom: var(--space-6);
}

.page-hero__number {
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
  letter-spacing: var(--tracking-wider);
  color: var(--text-muted);
  margin-bottom: var(--space-6);
  display: block;
}

.page-hero__title {
  font-size: var(--text-5xl);
  margin-bottom: var(--space-6);
}

.page-hero__description {
  font-size: var(--text-xl);
  line-height: var(--leading-normal);
  color: var(--text-secondary);
  max-width: 52ch;
}

/* ---- Grid Systems ---- */
.grid {
  display: grid;
  gap: var(--space-6);
}

.grid--2 {
  grid-template-columns: repeat(2, 1fr);
}

.grid--3 {
  grid-template-columns: repeat(3, 1fr);
}

.grid--4 {
  grid-template-columns: repeat(4, 1fr);
}

.grid--auto {
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
}

/* ---- Two Column Content ---- */
.two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-12);
  align-items: start;
}

.two-col--wide-left {
  grid-template-columns: 2fr 1fr;
}

.two-col--wide-right {
  grid-template-columns: 1fr 2fr;
}

/* ---- Bento Grid ---- */
.bento {
  display: grid;
  gap: var(--space-4);
}

.bento--mosaic {
  grid-template-columns: repeat(3, 1fr);
  grid-auto-rows: minmax(200px, auto);
}

.bento__item--hero {
  grid-column: span 2;
  grid-row: span 2;
}

.bento__item--tall {
  grid-row: span 2;
}

.bento__item--wide {
  grid-column: span 2;
}

/* ---- Asset Rows (per-item layout) ---- */
.asset-rows {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

.asset-row {
  display: grid;
  gap: var(--space-6);
}

.asset-row--full {
  grid-template-columns: 1fr;
}

.asset-row--split {
  grid-template-columns: repeat(2, 1fr);
}

.asset-item {
  display: flex;
  flex-direction: column;
}

/* ---- Bottom Navigation (Prev/Next) ---- */
.page-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-10) var(--page-gutter);
  max-width: var(--content-width);
  margin: 0 auto;
}

.page-nav__link {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  text-decoration: none;
  transition: opacity var(--duration-fast) var(--ease-default);
  max-width: 45%;
}

.page-nav__link:hover {
  opacity: 0.6;
}

.page-nav__link--next {
  align-items: flex-end;
  text-align: right;
  margin-left: auto;
}

.page-nav__label {
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  letter-spacing: var(--tracking-widest);
  text-transform: uppercase;
  color: var(--text-muted);
}

.page-nav__title {
  font-family: var(--font-heading);
  font-size: var(--text-2xl);
  font-weight: var(--weight-semibold);
  color: var(--text-primary);
}

/* ---- Divider ---- */
.divider {
  border: none;
  border-top: 1px solid var(--border-default);
  margin: var(--space-16) 0;
}

.divider--subtle {
  border-color: var(--border-subtle);
}

/* ---- Responsive ---- */
@media (max-width: 1024px) {
  .grid--4 {
    grid-template-columns: repeat(2, 1fr);
  }
  .grid--3 {
    grid-template-columns: repeat(2, 1fr);
  }
  .two-col {
    grid-template-columns: 1fr;
    gap: var(--space-8);
  }
  .two-col--wide-left,
  .two-col--wide-right {
    grid-template-columns: 1fr;
  }
  .bento--mosaic {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 767px) {
  .grid--2,
  .grid--3,
  .grid--4 {
    grid-template-columns: 1fr;
  }
  .asset-row--split {
    grid-template-columns: 1fr;
  }
  .bento--mosaic {
    grid-template-columns: 1fr;
  }
  .bento__item--hero,
  .bento__item--tall,
  .bento__item--wide {
    grid-column: span 1;
    grid-row: span 1;
  }
  .page-nav {
    flex-direction: column;
    gap: var(--space-8);
    align-items: stretch;
  }
  .page-nav__link--next {
    align-items: flex-start;
    text-align: left;
  }
}

@media (min-width: 1600px) {
  .page__main {
    padding-top: calc(var(--space-24) + var(--space-8));
  }
}