/* =============================================================================
   LAYOUT.CSS — SPA Layout, Progress Bar, Content Container, Sidebar Drawer
   HTTP Learning Portal
   ============================================================================= */

/* --- App Shell ------------------------------------------------------------- */
.app {
  display: flex;
  flex-direction: column;
  height: 100%;
  overflow-y: auto;
  background-color: var(--color-bg-primary);
}

/* --- Top Header (Progress Bar) --------------------------------------------- */
.app-header {
  position: sticky;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  padding: 0 var(--space-4);
  background-color: var(--color-bg-surface);
  border-bottom: 1px solid var(--color-border-primary);
  z-index: var(--z-index-sticky);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.menu-btn {
  background: transparent;
  border: 1px solid var(--color-border-primary);
  color: var(--color-text-secondary);
  border-radius: var(--radius-md);
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.menu-btn:hover {
  background: var(--color-bg-secondary);
  color: var(--color-text-primary);
}

.app-header__brand {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-weight: var(--font-weight-bold);
  font-size: var(--font-size-base);
  color: var(--color-text-primary);
  text-decoration: none;
}

.app-header__brand:hover {
  text-decoration: none;
}

.app-header__logo-icon {
  width: 28px;
  height: 28px;
  background: linear-gradient(135deg, var(--color-accent-primary), #a855f7);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-bold);
}

.app-header__progress-container {
  flex: 1;
  max-width: 400px;
  margin: 0 var(--space-4);
  display: flex;
  flex-direction: column;
  gap: 4px;
}

@media (max-width: 600px) {
  .app-header__progress-container {
    display: none; /* Hide on very small screens, show progress text instead */
  }
}

.app-header__progress-text {
  display: flex;
  justify-content: space-between;
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
}

.app-header__progress-bar {
  height: 6px;
  background-color: var(--color-bg-secondary);
  border-radius: 3px;
  overflow: hidden;
}

.app-header__progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--color-accent-primary), #a855f7);
  width: 0%;
  transition: width var(--transition-normal) ease-out;
}

.app-header__actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

/* --- Sidebar Drawer -------------------------------------------------------- */
.sidebar-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  backdrop-filter: blur(4px);
  z-index: var(--z-index-modal);
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-normal);
}

.sidebar-overlay.is-open {
  opacity: 1;
  visibility: visible;
}

.sidebar-drawer {
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  width: 300px;
  background: var(--color-bg-surface);
  border-right: 1px solid var(--color-border-primary);
  z-index: calc(var(--z-index-modal) + 1);
  transform: translateX(-100%);
  transition: transform var(--transition-normal) cubic-bezier(0.16, 1, 0.3, 1);
  display: flex;
  flex-direction: column;
  box-shadow: var(--shadow-xl);
}

.sidebar-drawer.is-open {
  transform: translateX(0);
}

.sidebar-drawer__header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-4);
  border-bottom: 1px solid var(--color-border-primary);
}

.sidebar-drawer__title {
  font-weight: var(--font-weight-bold);
  font-size: var(--font-size-lg);
  color: var(--color-text-primary);
}

.sidebar-drawer__close {
  background: transparent;
  border: none;
  font-size: 24px;
  color: var(--color-text-muted);
  cursor: pointer;
  line-height: 1;
}

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

.sidebar-drawer__content {
  flex: 1;
  overflow-y: auto;
  padding: var(--space-4);
}

.nav-chapter {
  margin-bottom: var(--space-6);
}

.nav-chapter__title {
  font-size: var(--font-size-xs);
  font-weight: 700;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--space-2);
}

.nav-item {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2);
  border-radius: var(--radius-sm);
  color: var(--color-text-secondary);
  text-decoration: none;
  font-size: var(--font-size-sm);
  transition: all var(--transition-fast);
}

.nav-item:hover {
  background: var(--color-bg-secondary);
  color: var(--color-text-primary);
  text-decoration: none;
}

.nav-item.is-active {
  background: rgba(88, 166, 255, 0.1);
  color: var(--color-accent-primary);
  font-weight: 600;
}

.nav-item__number {
  background: var(--color-bg-tertiary);
  color: var(--color-text-muted);
  font-size: 10px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
}

.nav-item.is-active .nav-item__number {
  background: var(--color-accent-primary);
  color: white;
}

/* --- Main Content Area ----------------------------------------------------- */
.main-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  padding: var(--space-4);
  padding-bottom: 80px; /* Space for bottom nav */
  position: relative;
}

.page-container {
  width: 100%;
  max-width: 800px;
  margin: 0 auto;
}

/* --- Chapter & Step Headers ------------------------------------------------ */
.chapter-label {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-accent-primary);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-4);
}

.step-title {
  font-size: var(--font-size-3xl);
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
  margin-bottom: var(--space-6);
  line-height: 1.2;
}

.mdn-reference a:hover {
  color: var(--color-accent-primary) !important;
}

@media (max-width: 600px) {
  .step-title {
    font-size: var(--font-size-2xl);
  }
}

/* --- Bottom Navigation ----------------------------------------------------- */
.bottom-nav {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background-color: var(--color-bg-surface);
  border-top: 1px solid var(--color-border-primary);
  padding: var(--space-3) var(--space-4);
  display: flex;
  justify-content: center;
  z-index: var(--z-index-sticky);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
}

.bottom-nav__container {
  width: 100%;
  max-width: 800px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.bottom-nav__step-indicator {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-text-secondary);
}

@media (max-width: 600px) {
  .bottom-nav__step-indicator {
    display: none;
  }
}

/* --- Layout Utilities ------------------------------------------------------ */
.stack {
  display: flex;
  flex-direction: column;
  gap: var(--space-5);
}

.stack-sm {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.stack-lg {
  display: flex;
  flex-direction: column;
  gap: var(--space-8);
}

.divider {
  border: none;
  border-top: 1px solid var(--color-border-primary);
  margin: var(--space-8) 0;
}