/* ============================================
   Layout System
   ============================================ */

/* === App Layout === */
#app {
  max-width: 428px;
  margin: 0 auto;
  min-height: 100vh;
  background-color: var(--color-bg);
  position: relative;
  overflow-x: hidden;
}

.app-header {
  position: sticky;
  top: 0;
  z-index: var(--z-header);
  background: var(--color-bg-white);
  height: var(--header-height);
  display: flex;
  align-items: center;
  padding: 0 var(--space-md);
  border-bottom: 1px solid var(--color-border-light);
}

.app-header__title {
  font-size: var(--text-h3-size);
  font-weight: var(--text-h3-weight);
  flex: 1;
  text-align: center;
}

.app-header__left,
.app-header__right {
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.app-main {
  min-height: calc(100vh - var(--header-height) - var(--bottom-nav-height));
  padding-bottom: var(--bottom-nav-height);
}

.app-main--no-header {
  min-height: calc(100vh - var(--bottom-nav-height));
}

.app-main--no-nav {
  min-height: calc(100vh - var(--header-height));
  padding-bottom: 0;
}

.app-main--fullscreen {
  min-height: 100vh;
  padding-bottom: 0;
}

/* === Screen Container === */
.screen {
  padding: var(--space-md);
  animation: fadeIn var(--transition-normal);
}

.screen--no-padding {
  padding: 0;
}

.screen__section {
  margin-bottom: var(--space-lg);
}

.screen__section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-md);
  padding: 0 var(--space-md);
}

.screen__section-title {
  font-size: var(--text-h3-size);
  font-weight: var(--text-h3-weight);
}

.screen__section-action {
  font-size: var(--text-body-sm-size);
  color: var(--color-primary);
  font-weight: 500;
}

/* === Grid System === */
.grid {
  display: grid;
  gap: var(--space-md);
}

.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }

/* === Flex Utilities === */
.flex { display: flex; }
.flex-col { flex-direction: column; }
.flex-wrap { flex-wrap: wrap; }
.items-center { align-items: center; }
.items-start { align-items: flex-start; }
.items-end { align-items: flex-end; }
.items-stretch { align-items: stretch; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.justify-end { justify-content: flex-end; }
.flex-1 { flex: 1; }
.flex-shrink-0 { flex-shrink: 0; }

.gap-xs { gap: var(--space-xs); }
.gap-sm { gap: var(--space-sm); }
.gap-md { gap: var(--space-md); }
.gap-lg { gap: var(--space-lg); }

/* === Spacing Utilities === */
.p-0 { padding: 0; }
.p-xs { padding: var(--space-xs); }
.p-sm { padding: var(--space-sm); }
.p-md { padding: var(--space-md); }
.p-lg { padding: var(--space-lg); }
.p-xl { padding: var(--space-xl); }

.px-md { padding-left: var(--space-md); padding-right: var(--space-md); }
.px-lg { padding-left: var(--space-lg); padding-right: var(--space-lg); }
.py-sm { padding-top: var(--space-sm); padding-bottom: var(--space-sm); }
.py-md { padding-top: var(--space-md); padding-bottom: var(--space-md); }
.py-lg { padding-top: var(--space-lg); padding-bottom: var(--space-lg); }

.m-0 { margin: 0; }
.mb-xs { margin-bottom: var(--space-xs); }
.mb-sm { margin-bottom: var(--space-sm); }
.mb-md { margin-bottom: var(--space-md); }
.mb-lg { margin-bottom: var(--space-lg); }
.mb-xl { margin-bottom: var(--space-xl); }
.mt-sm { margin-top: var(--space-sm); }
.mt-md { margin-top: var(--space-md); }
.mt-lg { margin-top: var(--space-lg); }

/* === Width Utilities === */
.w-full { width: 100%; }
.w-auto { width: auto; }

/* === Display Utilities === */
.hidden { display: none !important; }
.block { display: block; }
.inline-block { display: inline-block; }

/* === Overflow === */
.overflow-hidden { overflow: hidden; }
.overflow-auto { overflow: auto; }
.overflow-x-auto {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
}
.overflow-x-auto::-webkit-scrollbar { display: none; }

/* === Horizontal Scroll Row === */
.scroll-row {
  display: flex;
  gap: var(--space-md);
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scroll-snap-type: x mandatory;
  padding: 0 var(--space-md);
  scrollbar-width: none;
}

.scroll-row::-webkit-scrollbar {
  display: none;
}

.scroll-row > * {
  scroll-snap-align: start;
  flex-shrink: 0;
}

/* === Card === */
.card {
  background: var(--color-surface);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-md);
  overflow: hidden;
}

.card--flat {
  box-shadow: none;
  border: 1px solid var(--color-border-light);
}

.card--interactive {
  cursor: pointer;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.card--interactive:active {
  transform: scale(0.98);
  box-shadow: var(--shadow-sm);
}

/* === Divider === */
.divider {
  height: 1px;
  background: var(--color-divider);
  border: none;
}

.divider--thick {
  height: 8px;
  background: var(--color-bg);
}

/* === Safe Area === */
.safe-bottom {
  padding-bottom: max(var(--space-md), env(safe-area-inset-bottom));
}

.safe-top {
  padding-top: max(var(--space-md), env(safe-area-inset-top));
}

/* === Position Utilities === */
.relative { position: relative; }
.absolute { position: absolute; }
.fixed { position: fixed; }
.sticky { position: sticky; }

/* === Rounded === */
.rounded { border-radius: var(--radius-md); }
.rounded-sm { border-radius: var(--radius-sm); }
.rounded-lg { border-radius: var(--radius-lg); }
.rounded-full { border-radius: var(--radius-full); }

/* === Backdrop for overlays === */
.backdrop {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.5);
  z-index: var(--z-overlay);
  animation: fadeIn var(--transition-fast);
}

/* === Responsive: Narrow Screens (320px) === */
@media (max-width: 359px) {
  .grid-2 {
    grid-template-columns: 1fr;
  }

  .scroll-row {
    gap: var(--space-sm);
    padding: 0 var(--space-sm);
  }

  .screen {
    padding: var(--space-sm);
  }

  .screen__section-header {
    padding: 0 var(--space-sm);
  }
}