/**
 * HabitFlow - Header & Navigation Styles
 * Desktop navigation, mobile header, hamburger drawer, and theme toggler.
 */

.site-header {
  position: sticky;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background-color: rgba(248, 250, 252, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  transition: background-color var(--transition-base), border-color var(--transition-base);
}

[data-theme="dark"] .site-header {
  background-color: rgba(9, 13, 22, 0.85);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
  gap: var(--space-4);
}

/* Brand Logo */
.brand-logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  text-decoration: none;
  font-size: 1.35rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  color: var(--text);
  user-select: none;
}

.brand-icon {
  width: 34px;
  height: 34px;
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #ffffff;
  font-size: 1.1rem;
  box-shadow: 0 4px 10px var(--primary-glow);
}

/* Desktop Nav */
.desktop-nav {
  display: none;
}

@media (min-width: 1024px) {
  .desktop-nav {
    display: flex;
    align-items: center;
    gap: var(--space-6);
  }
}

.nav-link {
  font-size: 0.925rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: color var(--transition-fast);
  padding: var(--space-1) 0;
  position: relative;
}

.nav-link:hover {
  color: var(--primary);
}

.nav-link.active {
  color: var(--primary);
  font-weight: 600;
}

/* Header Actions */
.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.login-link {
  display: none;
  font-size: 0.925rem;
  font-weight: 600;
  color: var(--text);
  padding: 0.6rem 1rem;
  transition: color var(--transition-fast);
}

@media (min-width: 640px) {
  .login-link {
    display: inline-flex;
    align-items: center;
  }
}

.login-link:hover {
  color: var(--primary);
}

/* Theme Toggle Button */
.theme-toggle-btn {
  width: 40px;
  height: 40px;
  min-height: 40px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--surface-secondary);
  color: var(--text);
  border: 1px solid var(--border);
  transition: all var(--transition-fast);
}

.theme-toggle-btn:hover {
  background-color: var(--surface-muted);
  transform: rotate(15deg);
}

.theme-toggle-btn svg {
  width: 20px;
  height: 20px;
  stroke: currentColor;
}

/* Hamburger Button */
.mobile-menu-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  border-radius: var(--radius-md);
  background-color: var(--surface-secondary);
  border: 1px solid var(--border);
  color: var(--text);
  cursor: pointer;
}

@media (min-width: 1024px) {
  .mobile-menu-toggle {
    display: none;
  }
}

/* Mobile Drawer */
.mobile-drawer-backdrop {
  position: fixed;
  inset: 0;
  background-color: rgba(15, 23, 42, 0.6);
  backdrop-filter: blur(4px);
  z-index: 1100;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-base);
}

.mobile-drawer-backdrop.open {
  opacity: 1;
  pointer-events: auto;
}

.mobile-drawer {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  width: 85%;
  max-width: 360px;
  background-color: var(--surface);
  border-left: 1px solid var(--border);
  z-index: 1200;
  transform: translateX(100%);
  transition: transform var(--transition-smooth);
  display: flex;
  flex-direction: column;
  padding: var(--space-6);
  padding-bottom: calc(var(--space-6) + var(--safe-bottom));
  overflow-y: auto;
}

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

.drawer-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-6);
  padding-bottom: var(--space-4);
  border-bottom: 1px solid var(--border);
}

.drawer-nav {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  margin-bottom: auto;
}

.drawer-link {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text);
  padding: 0.75rem var(--space-3);
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast);
}

.drawer-link:hover,
.drawer-link:active {
  background-color: var(--surface-secondary);
  color: var(--primary);
}

.drawer-footer {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  padding-top: var(--space-6);
  border-top: 1px solid var(--border);
}