/**
 * Babel Flash - Core Stylesheet
 * Light and bright, modern minimalistic, flat UI design.
 */

:root {
  /* Flat Minimalist Palette */
  --bg-page: #f8fafc;
  --bg-surface: #ffffff;
  --bg-surface-subtle: #f1f5f9;
  --bg-surface-active: #e2e8f0;

  --border-light: #e2e8f0;
  --border-medium: #cbd5e1;
  --border-focus: #3b82f6;

  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --text-white: #ffffff;

  /* Brand Accents */
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-light: #eff6ff;

  --greek-accent: #0284c7;
  --greek-light: #f0f9ff;
  --hebrew-accent: #7c3aed;
  --hebrew-light: #faf5ff;

  --success: #16a34a;
  --success-light: #f0fdf4;
  --warning: #d97706;
  --warning-light: #fffbeb;
  --danger: #dc2626;
  --danger-light: #fef2f2;

  /* Typography */
  --font-sans: 'Plus Jakarta Sans', system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-greek: 'SBL Greek', 'Cardo', 'GFS Didot', 'Gentium Plus', 'Palatino Linotype', Georgia, serif;
  --font-hebrew: 'SBL Hebrew', 'Ezra SIL', 'David Libre', 'Frank Ruehl CLM', 'Times New Roman', serif;

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s ease;

  /* Dimensions */
  --sidebar-width: 260px;
  --header-height: 64px;
}

/* CSS Reset & Base */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-page);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Typography Helpers */
h1, h2, h3, h4, h5, h6 {
  color: var(--text-primary);
  font-weight: 700;
  line-height: 1.25;
}

p {
  margin-bottom: 1rem;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--primary-hover);
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

/* App Shell Layout */
.app-layout {
  display: flex;
  min-height: 100vh;
}

/* Desktop Sidebar */
.app-sidebar {
  width: var(--sidebar-width);
  background: var(--bg-surface);
  border-right: 1px solid var(--border-light);
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  z-index: 100;
}

.sidebar-header {
  height: var(--header-height);
  padding: 0 20px;
  display: flex;
  align-items: center;
  border-bottom: 1px solid var(--border-light);
}

.brand-link {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 20px;
  font-weight: 800;
  color: var(--text-primary);
  letter-spacing: -0.02em;
}

.brand-icon {
  width: 32px;
  height: 32px;
  background: var(--primary);
  color: white;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  font-weight: 700;
}

.sidebar-nav {
  padding: 20px 12px;
  flex: 1;
  overflow-y: auto;
}

.nav-section-title {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  font-weight: 700;
  padding: 10px 12px 6px 12px;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 14px;
  border-radius: 8px;
  color: var(--text-secondary);
  font-size: 14px;
  font-weight: 500;
  transition: all var(--transition-fast);
  margin-bottom: 4px;
  cursor: pointer;
}

.nav-item:hover {
  background: var(--bg-surface-subtle);
  color: var(--text-primary);
}

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

.nav-item svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.sidebar-footer {
  padding: 16px 20px;
  border-top: 1px solid var(--border-light);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.user-profile-badge {
  display: flex;
  align-items: center;
  gap: 10px;
}

.user-avatar {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--bg-surface-subtle);
  border: 1px solid var(--border-light);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  color: var(--primary);
  font-size: 14px;
}

.user-info-text {
  font-size: 13px;
  line-height: 1.2;
}

.user-info-text .name {
  font-weight: 600;
  color: var(--text-primary);
}

.user-info-text .tier {
  font-size: 11px;
  color: var(--text-muted);
}

/* Main Content Area */
.app-main {
  flex: 1;
  min-width: 0;
  margin-left: var(--sidebar-width);
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* Top App Bar */
.app-header {
  height: var(--header-height);
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border-light);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 32px;
  position: sticky;
  top: 0;
  z-index: 50;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 16px;
}

.header-title {
  font-size: 18px;
  font-weight: 700;
  color: var(--text-primary);
}

.header-right {
  display: flex;
  align-items: center;
  gap: 16px;
}

.streak-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--warning-light);
  color: var(--warning);
  padding: 6px 12px;
  border-radius: 20px;
  font-size: 13px;
  font-weight: 600;
  border: 1px solid #fde68a;
}

.progress-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--success-light);
  color: var(--success);
  padding: 6px 12px;
  border-radius: 20px;
  font-size: 13px;
  font-weight: 600;
  border: 1px solid #bbf7d0;
}

/* Content Container */
.app-content {
  padding: 32px;
  max-width: 1200px;
  width: 100%;
  margin: 0 auto;
}

/* Flat Button System */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 18px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  border: 1px solid transparent;
  line-height: 1;
}

.btn-primary {
  background: var(--primary);
  color: white;
}

.btn-primary:hover {
  background: var(--primary-hover);
  color: white;
}

.btn-outline {
  background: var(--bg-surface);
  color: var(--text-primary);
  border-color: var(--border-light);
}

.btn-outline:hover {
  background: var(--bg-surface-subtle);
  border-color: var(--border-medium);
}

.btn-ghost {
  color: var(--text-secondary);
}

.btn-ghost:hover {
  background: var(--bg-surface-subtle);
  color: var(--text-primary);
}

.btn-sm {
  padding: 6px 12px;
  font-size: 13px;
  border-radius: 6px;
}

.btn-lg {
  padding: 14px 24px;
  font-size: 16px;
  border-radius: 10px;
}

/* Flat Surface Cards */
.card-panel {
  background: var(--bg-surface);
  border: 1px solid var(--border-light);
  border-radius: 12px;
  padding: 24px;
  margin-bottom: 24px;
}

/* Deck Grid */
.decks-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 20px;
  margin-top: 16px;
}

.deck-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-light);
  border-radius: 12px;
  padding: 20px;
  transition: all var(--transition-fast);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  cursor: pointer;
  position: relative;
  overflow: hidden;
}

.deck-card:hover {
  border-color: var(--border-medium);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.04);
  transform: translateY(-2px);
}

.deck-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
}

.deck-card.lang-greek::before {
  background: var(--greek-accent);
}

.deck-card.lang-hebrew::before {
  background: var(--hebrew-accent);
}

.deck-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  margin-bottom: 12px;
}

.deck-badge {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 4px 8px;
  border-radius: 6px;
}

.badge-greek {
  background: var(--greek-light);
  color: var(--greek-accent);
}

.badge-hebrew {
  background: var(--hebrew-light);
  color: var(--hebrew-accent);
}

.deck-title {
  font-size: 17px;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 6px;
}

.deck-desc {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.5;
  margin-bottom: 18px;
}

.deck-stats {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-top: 1px solid var(--border-light);
  padding-top: 14px;
  font-size: 13px;
  color: var(--text-muted);
}

.deck-progress-bar {
  height: 6px;
  background: var(--bg-surface-subtle);
  border-radius: 3px;
  overflow: hidden;
  margin-top: 8px;
}

.deck-progress-fill {
  height: 100%;
  background: var(--success);
  border-radius: 3px;
  transition: width 0.3s ease;
}

/* Modals */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(15, 23, 42, 0.4);
  backdrop-filter: blur(2px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-fast);
  padding: 20px;
}

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

.modal-window {
  background: var(--bg-surface);
  border: 1px solid var(--border-light);
  border-radius: 14px;
  max-width: 520px;
  width: 100%;
  max-height: 90vh;
  overflow-y: auto;
  padding: 32px;
  box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  transform: translateY(10px);
  transition: transform var(--transition-fast);
}

.modal-overlay.open .modal-window {
  transform: translateY(0);
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
}

.modal-title {
  font-size: 20px;
  font-weight: 700;
}

.close-btn {
  font-size: 24px;
  color: var(--text-muted);
  cursor: pointer;
  line-height: 1;
}

.close-btn:hover {
  color: var(--text-primary);
}

/* Form Styles */
.form-group {
  margin-bottom: 18px;
}

.form-label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 6px;
}

.form-input, .form-select {
  width: 100%;
  padding: 10px 14px;
  border: 1px solid var(--border-light);
  border-radius: 8px;
  font-family: inherit;
  font-size: 14px;
  background: var(--bg-surface);
  color: var(--text-primary);
  transition: border-color var(--transition-fast);
}

.form-input:focus, .form-select:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-checkbox-label {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 14px;
  cursor: pointer;
  user-select: none;
}

/* Mobile Bottom Navigation */
.mobile-nav {
  display: none;
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: 60px;
  background: var(--bg-surface);
  border-top: 1px solid var(--border-light);
  z-index: 90;
  justify-content: space-around;
  align-items: center;
}

.mobile-nav-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  color: var(--text-muted);
  font-size: 11px;
  font-weight: 600;
  flex: 1;
  height: 100%;
}

.mobile-nav-item.active {
  color: var(--primary);
}

/* Responsive Breakpoints */
.btn-danger {
  background: #dc2626;
  color: #ffffff;
}

.btn-danger:hover {
  background: #b91c1c;
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

/* Study filter segmented control */
.study-filter-pills {
  display: flex;
  align-items: center;
  gap: 6px;
  background: #e2e8f0;
  padding: 3px;
  border-radius: 8px;
}

.filter-pill {
  padding: 4px 10px;
  font-size: 12px;
  background: transparent;
  color: var(--text-secondary);
}

.filter-pill:hover {
  color: var(--text-primary);
}

.filter-pill.active {
  background: var(--bg-surface);
  color: var(--primary);
  box-shadow: 0 1px 2px rgba(15, 23, 42, 0.12);
}

.deck-card:focus-visible,
.nav-item:focus-visible,
.close-btn:focus-visible {
  outline: 3px solid var(--border-focus);
  outline-offset: 2px;
}

@media (max-width: 860px) {
  .app-sidebar {
    display: none;
  }
  .app-main {
    margin-left: 0;
    margin-bottom: 60px;
  }
  .mobile-nav {
    display: flex;
  }
  .app-header {
    height: auto;
    min-height: var(--header-height);
    flex-wrap: wrap;
    gap: 8px;
    padding: 12px 16px;
  }
  .app-content {
    padding: 20px 16px;
  }
  .decks-grid {
    grid-template-columns: 1fr;
  }
  .study-deck-heading {
    flex-wrap: wrap;
    max-width: 100%;
  }
  .study-filter-pills {
    flex-wrap: wrap;
    max-width: 100%;
  }
}