/* ==========================================================================
   StudyPulse AI - Modern Dark Aesthetic Design System
   ========================================================================== */

:root {
  --bg-primary: #0a0d14;
  --bg-secondary: #111622;
  --bg-card: rgba(22, 29, 44, 0.75);
  --bg-card-hover: rgba(28, 37, 56, 0.85);
  --bg-input: #0e131d;
  
  --border-color: rgba(255, 255, 255, 0.08);
  --border-glow: rgba(99, 102, 241, 0.4);
  --border-accent: rgba(99, 102, 241, 0.2);

  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;

  --accent-primary: #6366f1;
  --accent-gradient: linear-gradient(135deg, #6366f1 0%, #8b5cf6 50%, #d946ef 100%);
  --accent-hover: #4f46e5;
  --accent-cyan: #06b6d4;
  --accent-emerald: #10b981;
  --accent-amber: #f59e0b;
  --accent-rose: #f43f5e;

  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-display: 'Outfit', var(--font-sans);
  --font-mono: 'JetBrains Mono', monospace;

  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.25);
  --shadow-md: 0 4px 14px rgba(0, 0, 0, 0.35);
  --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 24px rgba(99, 102, 241, 0.25);

  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  --transition-fast: 0.18s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-smooth: 0.35s cubic-bezier(0.16, 1, 0.3, 1);
}

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

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background-image: 
    radial-gradient(circle at 15% 10%, rgba(99, 102, 241, 0.08) 0%, transparent 40%),
    radial-gradient(circle at 85% 80%, rgba(6, 182, 212, 0.06) 0%, transparent 40%);
  background-attachment: fixed;
  -webkit-font-smoothing: antialiased;
}

.app-container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 1.5rem 2rem;
  width: 100%;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* Typography Helpers */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.02em;
}

.gradient-text {
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.text-muted { color: var(--text-muted); }
.text-sm { font-size: 0.875rem; }
.text-xs { font-size: 0.75rem; }

/* Header */
.header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--border-color);
  margin-bottom: 1.75rem;
  flex-wrap: wrap;
  gap: 1rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.logo-badge {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  background: var(--accent-gradient);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  box-shadow: var(--shadow-glow);
  animation: pulse-logo 4s ease-in-out infinite alternate;
}

@keyframes pulse-logo {
  0% { transform: scale(1); box-shadow: 0 0 20px rgba(99, 102, 241, 0.3); }
  100% { transform: scale(1.05); box-shadow: 0 0 30px rgba(217, 70, 239, 0.45); }
}

.brand-title {
  font-size: 1.75rem;
  line-height: 1.2;
}

.brand-subtitle {
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.header-badges {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.badge {
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
}

.badge-hf {
  background: rgba(245, 158, 11, 0.12);
  color: #fbbf24;
  border: 1px solid rgba(245, 158, 11, 0.3);
}

/* Buttons */
.btn {
  font-family: var(--font-sans);
  font-size: 0.875rem;
  font-weight: 600;
  padding: 0.6rem 1.2rem;
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  transition: all var(--transition-fast);
}

.btn-primary {
  background: var(--accent-gradient);
  color: #fff;
  box-shadow: 0 4px 15px rgba(99, 102, 241, 0.35);
}

.btn-primary:hover {
  opacity: 0.95;
  transform: translateY(-1px);
  box-shadow: 0 6px 20px rgba(99, 102, 241, 0.5);
}

.btn-secondary {
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
  backdrop-filter: blur(8px);
}

.btn-secondary:hover {
  background: rgba(255, 255, 255, 0.09);
  border-color: rgba(255, 255, 255, 0.18);
}

.btn-sm {
  padding: 0.4rem 0.8rem;
  font-size: 0.8rem;
}

.btn-lg {
  padding: 0.85rem 1.75rem;
  font-size: 1rem;
}

.btn-block {
  width: 100%;
}

.btn-success {
  background: rgba(16, 185, 129, 0.15);
  color: #34d399;
  border: 1px solid rgba(16, 185, 129, 0.3);
}
.btn-success:hover {
  background: rgba(16, 185, 129, 0.25);
}

.btn-danger {
  background: rgba(244, 63, 94, 0.15);
  color: #fb7185;
  border: 1px solid rgba(244, 63, 94, 0.3);
}
.btn-danger:hover {
  background: rgba(244, 63, 94, 0.25);
}

.btn-text {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  transition: color var(--transition-fast);
}
.btn-text:hover {
  color: var(--text-primary);
}

.btn-icon {
  background: none;
  border: none;
  font-size: 1.5rem;
  color: var(--text-muted);
  cursor: pointer;
  line-height: 1;
}
.btn-icon:hover {
  color: var(--text-primary);
}

/* Main Layout Grid */
.main-layout {
  display: grid;
  grid-template-columns: 1fr 1.25fr;
  gap: 1.75rem;
  flex: 1;
  align-items: start;
}

@media (max-width: 1024px) {
  .main-layout {
    grid-template-columns: 1fr;
  }
}

/* Glassmorphic Panels */
.panel {
  background: var(--bg-card);
  backdrop-filter: blur(16px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  padding: 1.75rem;
  box-shadow: var(--shadow-md);
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  transition: border-color var(--transition-smooth);
}

.panel:hover {
  border-color: rgba(255, 255, 255, 0.12);
}

.panel-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.panel-header h2 {
  font-size: 1.25rem;
}

/* Sample Pills */
.sample-pills {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  flex-wrap: wrap;
}

.pill-label {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.pill {
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  font-size: 0.72rem;
  padding: 0.25rem 0.6rem;
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.pill:hover {
  background: rgba(99, 102, 241, 0.15);
  color: #a5b4fc;
  border-color: var(--border-accent);
}

/* Textarea & Inputs */
.textarea-container {
  display: flex;
  flex-direction: column;
  background: var(--bg-input);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.textarea-container:focus-within {
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

textarea#notes-input {
  width: 100%;
  height: 280px;
  background: transparent;
  border: none;
  padding: 1rem;
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 0.9rem;
  line-height: 1.6;
  resize: vertical;
  outline: none;
}

textarea#notes-input::placeholder {
  color: var(--text-muted);
}

.textarea-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.5rem 1rem;
  background: rgba(255, 255, 255, 0.02);
  border-top: 1px solid var(--border-color);
}

/* Controls */
.generation-controls {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.control-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

@media (max-width: 600px) {
  .control-row {
    grid-template-columns: 1fr;
  }
}

.control-item {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.control-item label {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-secondary);
}

.form-input {
  background: var(--bg-input);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 0.875rem;
  padding: 0.6rem 0.8rem;
  border-radius: var(--radius-md);
  outline: none;
  transition: border-color var(--transition-fast);
}

.form-input:focus {
  border-color: var(--accent-primary);
}

input[type="range"] {
  accent-color: var(--accent-primary);
  cursor: pointer;
  margin-top: 0.5rem;
}

/* Empty State */
.empty-state {
  text-align: center;
  padding: 3rem 1.5rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.empty-icon {
  font-size: 3rem;
  margin-bottom: 0.5rem;
  filter: drop-shadow(0 4px 12px rgba(0,0,0,0.4));
}

.empty-state h3 {
  font-size: 1.4rem;
}

.empty-state p {
  max-width: 480px;
  font-size: 0.9rem;
}

.feature-highlights {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1rem;
  width: 100%;
  margin-top: 1.5rem;
}

.feat-card {
  background: rgba(255, 255, 255, 0.025);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.25rem 1rem;
  text-align: left;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.feat-icon {
  font-size: 1.5rem;
  margin-bottom: 0.25rem;
}

.feat-card strong {
  font-size: 0.85rem;
  color: var(--text-primary);
}

.feat-card span {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* Loading State */
.loading-state {
  text-align: center;
  padding: 4rem 1.5rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.pulsing-brain {
  font-size: 3.5rem;
  animation: pulse-scale 1.5s infinite ease-in-out;
}

@keyframes pulse-scale {
  0% { transform: scale(0.92); opacity: 0.7; }
  50% { transform: scale(1.1); opacity: 1; filter: drop-shadow(0 0 20px rgba(99, 102, 241, 0.6)); }
  100% { transform: scale(0.92); opacity: 0.7; }
}

.progress-bar-container {
  width: 280px;
  height: 6px;
  background: rgba(255, 255, 255, 0.06);
  border-radius: var(--radius-full);
  overflow: hidden;
  margin-top: 0.5rem;
}

.progress-bar-fill {
  width: 100%;
  height: 100%;
  background: var(--accent-gradient);
  animation: indeterminate-progress 1.6s infinite ease-in-out;
  transform-origin: 0% 50%;
}

@keyframes indeterminate-progress {
  0% { transform: translateX(-100%); }
  50% { transform: translateX(0%); }
  100% { transform: translateX(100%); }
}

/* ==========================================================================
   3D Flip Flashcard Component
   ========================================================================== */
.card-scene {
  perspective: 1200px;
  width: 100%;
  margin: 1.25rem 0;
}

.flashcard {
  width: 100%;
  min-height: 280px;
  position: relative;
  transition: transform 0.65s cubic-bezier(0.4, 0, 0.2, 1);
  transform-style: preserve-3d;
  cursor: pointer;
}

.flashcard.is-flipped {
  transform: rotateY(180deg);
}

.card-face {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: var(--radius-lg);
  padding: 2rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-lg);
  background: linear-gradient(145deg, rgba(28, 36, 56, 0.8), rgba(18, 23, 38, 0.9));
  backdrop-filter: blur(12px);
}

.card-front {
  border-top: 3px solid var(--accent-primary);
}

.card-back {
  transform: rotateY(180deg);
  border-top: 3px solid var(--accent-emerald);
  background: linear-gradient(145deg, rgba(20, 38, 35, 0.8), rgba(14, 25, 26, 0.9));
}

.card-tag {
  align-self: flex-start;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 0.25rem 0.65rem;
  border-radius: var(--radius-full);
  background: rgba(99, 102, 241, 0.15);
  color: #a5b4fc;
}

.tag-answer {
  background: rgba(16, 185, 129, 0.15);
  color: #6ee7b7;
}

.card-content {
  margin: 1.5rem 0;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.card-text {
  font-size: 1.15rem;
  font-weight: 500;
  line-height: 1.6;
  color: var(--text-primary);
}

.card-analogy {
  background: rgba(245, 158, 11, 0.08);
  border-left: 3px solid var(--accent-amber);
  padding: 0.75rem 1rem;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  color: #fde68a;
  line-height: 1.5;
}

.card-hint {
  font-size: 0.75rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

/* Card Progress & Controls */
.deck-progress {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.deck-progress-bar {
  flex: 1;
  height: 6px;
  background: rgba(255, 255, 255, 0.08);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.deck-progress-fill {
  height: 100%;
  background: var(--accent-gradient);
  transition: width var(--transition-smooth);
}

.mastery-badge {
  font-size: 0.75rem;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-full);
  background: rgba(16, 185, 129, 0.12);
  color: #34d399;
  border: 1px solid rgba(16, 185, 129, 0.25);
}

.card-nav-controls {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  margin-top: 1rem;
}

.rating-buttons {
  display: flex;
  gap: 0.5rem;
}

/* Cards Grid Overview */
.deck-overview-section {
  margin-top: 2rem;
  border-top: 1px solid var(--border-color);
  padding-top: 1.25rem;
}

.section-title-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 0.75rem;
}

.mini-card {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 0.75rem;
  font-size: 0.8rem;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.mini-card:hover {
  background: rgba(255, 255, 255, 0.06);
  border-color: var(--accent-primary);
  transform: translateY(-2px);
}

.mini-card.active {
  border-color: var(--accent-primary);
  box-shadow: 0 0 12px rgba(99, 102, 241, 0.3);
}

.mini-card-q {
  font-weight: 600;
  margin-bottom: 0.4rem;
  color: var(--text-primary);
}

.mini-card-a {
  color: var(--text-muted);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

/* Quiz Interface */
.quiz-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.25rem;
}

.quiz-card {
  background: rgba(255, 255, 255, 0.025);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.quiz-question {
  font-size: 1.15rem;
  line-height: 1.5;
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.quiz-option {
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 0.9rem 1.25rem;
  text-align: left;
  color: var(--text-primary);
  font-size: 0.9rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.quiz-option:hover:not(.disabled) {
  background: rgba(99, 102, 241, 0.1);
  border-color: var(--accent-primary);
}

.quiz-option.correct {
  background: rgba(16, 185, 129, 0.15) !important;
  border-color: #10b981 !important;
  color: #34d399 !important;
}

.quiz-option.wrong {
  background: rgba(244, 63, 94, 0.15) !important;
  border-color: #f43f5e !important;
  color: #fb7185 !important;
}

.quiz-feedback {
  background: rgba(255, 255, 255, 0.04);
  border-radius: var(--radius-md);
  padding: 1rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

/* Cheatsheet / Text View */
.cheatsheet-card {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  line-height: 1.7;
}

.cheatsheet-card h3 {
  color: #a5b4fc;
  margin: 1.25rem 0 0.5rem 0;
  font-size: 1.15rem;
}

.cheatsheet-card ul {
  padding-left: 1.5rem;
  margin-bottom: 1rem;
}

.cheatsheet-card li {
  margin-bottom: 0.4rem;
  color: var(--text-secondary);
}

.cheatsheet-card strong {
  color: var(--text-primary);
}

/* Modal */
.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.75);
  backdrop-filter: blur(8px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: 1.5rem;
}

.modal-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  max-width: 500px;
  width: 100%;
  padding: 2rem;
  box-shadow: var(--shadow-lg);
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

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

.modal-title {
  font-size: 1.2rem;
}

.modal-body {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.form-group label {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-secondary);
}

.helper-text {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.status-box {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.6rem 0.8rem;
  background: rgba(255, 255, 255, 0.03);
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
}

.status-indicator {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--accent-emerald);
  box-shadow: 0 0 8px var(--accent-emerald);
}

/* Footer */
.footer {
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.text-right { text-align: right; }

/* Utilities */
.hidden { display: none !important; }