/* ==========================================================================
   layout.css — scroll-snap flow, nav, section frame, responsive grid
   ========================================================================== */

.scroll-container {
  height: 100dvh;
  overflow-y: auto;
  scroll-snap-type: y mandatory;
  scroll-behavior: smooth;
}

.section {
  position: relative;
  height: 100dvh;
  scroll-snap-align: start;
  scroll-snap-stop: always;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 6rem var(--section-pad-x) 3rem;
  overflow: hidden;
}

.section-inner {
  width: 100%;
  max-width: var(--max-content);
  margin: 0 auto;
}

/* Site navigation */
.site-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.5rem var(--section-pad-x);
  background: rgba(22, 22, 22, 0.85);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid rgba(58, 58, 58, 0.4);
}

.nav-mono {
  font-family: var(--font-mono);
  font-weight: 500;
  color: var(--color-text);
  letter-spacing: 0.05em;
}

.nav-list {
  display: flex;
  gap: 2rem;
}

.nav-list a {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--color-text);
  opacity: 0.55;
  transition: opacity var(--dur-fast) var(--ease-out);
  position: relative;
}

.nav-list a::after {
  content: '';
  position: absolute;
  left: 0;
  bottom: -6px;
  width: 100%;
  height: 1px;
  background: var(--color-text);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--dur-fast) var(--ease-out);
}

.nav-list a:hover,
.nav-list a.is-active {
  opacity: 1;
}

.nav-list a.is-active::after {
  transform: scaleX(1);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  z-index: 110;
}

.nav-toggle span {
  width: 22px;
  height: 2px;
  background: var(--color-text);
  transition: transform var(--dur-fast) var(--ease-out), opacity var(--dur-fast) var(--ease-out);
}

/* Nav overlay - hidden by default, shown on mobile when menu opens */
.nav-overlay {
  display: none;
}

/* Scroll cue (home only) */
.scroll-cue {
  position: absolute;
  bottom: 2.5rem;
  left: var(--section-pad-x);
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.5rem;
}

.scroll-cue-line {
  width: 1px;
  height: 40px;
  background: var(--color-gray-mid);
  overflow: hidden;
  position: relative;
}

.scroll-cue-line::after {
  content: '';
  position: absolute;
  top: -100%;
  left: 0;
  width: 100%;
  height: 100%;
  background: var(--color-text);
  animation: scrollCue 1.8s ease-in-out infinite;
}

@keyframes scrollCue {
  0% { top: -100%; }
  60% { top: 100%; }
  100% { top: 100%; }
}

/* Mobile nav */
@media (max-width: 768px) {
  .nav-toggle {
    display: flex;
    position: relative;
    z-index: 101;
  }

  .nav-overlay {
    display: block;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.7);
    opacity: 0;
    visibility: hidden;
    transition: opacity var(--dur-med) var(--ease-out), visibility var(--dur-med);
    z-index: 98;
    pointer-events: none;
  }

  .nav-overlay.is-open {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
  }

  .nav-list {
    position: fixed;
    top: 0;
    right: 0;
    height: 100dvh;
    width: min(75vw, 320px);
    background: var(--color-surface);
    flex-direction: column;
    justify-content: center;
    align-items: flex-start;
    gap: 1.75rem;
    padding: 2rem;
    transform: translateX(100%);
    transition: transform var(--dur-med) var(--ease-out);
    z-index: 99;
  }

  .nav-list.is-open {
    transform: translateX(0);
  }

  .nav-list a {
    font-size: 1rem;
    color: #fff;
  }

  .site-nav.is-open .nav-toggle span {
    background: #fff;
  }
}

@media (max-width: 768px) {
  .section {
    padding: 6.5rem 1.5rem 2.5rem;
    /* Top-align instead of center: when content is taller than the
       viewport, centering pushes overflow above the nav (getting clipped
       by .section's overflow:hidden). Top-aligning keeps headings visible. */
    align-items: flex-start;
  }
}