/* ==========================================================================
   layout.css — Page-level structural layout (header / footer shells,
   container, section rhythm). Component internals (nav, brand, footer
   links, cards, buttons) live in components.css.
   ========================================================================== */

/* ── Container ── */
.container {
  width: 100%;
  max-width: var(--width-max);
  margin-inline: auto;
  padding-inline: var(--spacing-lg);
}

@media (min-width: 768px) {
  .container {
    padding-inline: var(--spacing-xl);
  }
}

/* ── Site Header (shell only — nav internals in components.css) ── */
.site-header {
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  background: var(--color-surface-glass);
  backdrop-filter: var(--blur-md);
  -webkit-backdrop-filter: var(--blur-md);
  border-bottom: 1px solid transparent;
  transition:
    background var(--transition-base),
    box-shadow var(--transition-base),
    border-color var(--transition-base);
}

.site-header.is-scrolled {
  background: var(--color-surface-glass-stronger);
  border-bottom-color: var(--color-border);
  box-shadow: var(--shadow-md);
}

.header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-md);
  min-height: var(--height-header);
  padding-block: var(--spacing-sm);
}

/* ── Main content ── */
.site-main {
  display: block;
}

/* ── Section rhythm ── */
.section {
  padding-block: var(--spacing-3xl);
}

@media (min-width: 768px) {
  .section {
    padding-block: var(--spacing-4xl);
  }
}

.section--alt {
  background: var(--color-surface-glass);
}

.section__title {
  font-size: var(--font-size-2xl);
  font-weight: var(--font-weight-bold);
  color: var(--color-text);
  margin-bottom: var(--spacing-md);
}

.section__subtitle {
  color: var(--color-text-light);
  margin-bottom: var(--spacing-xl);
}

/* ── Site Footer (shell only — internals in components.css) ──
   Flat surface so the Courses CTA's soft-fade dissolves cleanly into the
   footer with no visible seam. Top margin + top padding zeroed so the
   footer sits flush against the fade; inner block owns its own
   padding-block. */
.site-footer {
  margin-top: 0;
  padding-block: 0;
  background: var(--color-surface);
}