/* ============================================================================
   TITO - Spaced Repetition Flashcard App
   A modern, beautiful design inspired by neon/cyberpunk aesthetics
   ============================================================================ */

/* CSS Variables / Theme */
:root {
    /* Colors - Cyberpunk/Neon Theme */
    --bg-primary: #0a0a0f;
    --bg-secondary: #12121a;
    --bg-tertiary: #1a1a25;
    --bg-card: #16161f;
    --bg-hover: #1f1f2c;
    
    /* Accent colors */
    --accent-primary: #00ffaa;
    --accent-secondary: #ff00aa;
    --accent-tertiary: #00aaff;
    --accent-warning: #ffaa00;
    --accent-danger: #ff4455;
    
    /* Text colors */
    --text-primary: #f0f0f5;
    --text-secondary: #a0a0b0;
    --text-muted: #606070;
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, var(--accent-primary), var(--accent-tertiary));
    --gradient-secondary: linear-gradient(135deg, var(--accent-secondary), var(--accent-warning));
    --gradient-bg: radial-gradient(ellipse at top, #15152a 0%, #0a0a0f 50%);
    
    /* Shadows & Effects */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.5);
    --shadow-glow: 0 0 20px rgba(0, 255, 170, 0.15);
    --shadow-glow-pink: 0 0 20px rgba(255, 0, 170, 0.15);
    
    /* Border radius */
    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --radius-xl: 28px;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 400ms ease;
    
    /* Typography */
    --font-primary: 'Outfit', system-ui, -apple-system, sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
    
    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    background: var(--gradient-bg);
    background-attachment: fixed;
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
}

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

.main-content {
    flex: 1;
    padding: var(--space-xl);
    padding-top: calc(70px + var(--space-xl));
    max-width: 1400px;
    margin: 0 auto;
    width: 100%;
}

/* ============================================================================
   Navigation
   ============================================================================ */

.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 70px;
    background: rgba(10, 10, 15, 0.85);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 var(--space-xl);
    z-index: 1000;
}

.navbar-brand {
    display: flex;
    align-items: center;
}

.navbar-logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    text-decoration: none;
    font-weight: 700;
    font-size: 1.5rem;
}

.logo-icon {
    font-size: 2rem;
}

.logo-text {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: 2px;
}

.navbar-menu {
    display: flex;
    gap: var(--space-sm);
}

.nav-link {
    display: flex;
    align-items: center;
    gap: var(--space-xs);
    padding: var(--space-sm) var(--space-md);
    text-decoration: none;
    color: var(--text-secondary);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    font-weight: 500;
}

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

.nav-link.active {
    background: rgba(0, 255, 170, 0.1);
    color: var(--accent-primary);
}

.nav-icon {
    font-size: 1.2rem;
}

/* ============================================================================
   Page Layout
   ============================================================================ */

.page {
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.page-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-xl);
    flex-wrap: wrap;
    gap: var(--space-md);
}

.page-header h1 {
    font-size: 2rem;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.header-back {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.header-actions {
    display: flex;
    gap: var(--space-sm);
}

/* ============================================================================
   Buttons
   ============================================================================ */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-lg);
    font-family: var(--font-primary);
    font-size: 0.95rem;
    font-weight: 500;
    text-decoration: none;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-primary {
    background: var(--gradient-primary);
    color: var(--bg-primary);
    box-shadow: var(--shadow-glow);
}

.btn-primary:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 0 30px rgba(0, 255, 170, 0.3);
}

.btn-secondary {
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.btn-secondary:hover:not(:disabled) {
    background: var(--bg-hover);
    border-color: rgba(255, 255, 255, 0.2);
}

.btn-danger {
    background: rgba(255, 68, 85, 0.15);
    color: var(--accent-danger);
    border: 1px solid rgba(255, 68, 85, 0.3);
}

.btn-danger:hover:not(:disabled) {
    background: rgba(255, 68, 85, 0.25);
}

.btn-icon {
    width: 40px;
    height: 40px;
    padding: 0;
    font-size: 1.1rem;
    background: transparent;
    color: var(--text-secondary);
}

.btn-icon:hover:not(:disabled) {
    background: var(--bg-hover);
    color: var(--text-primary);
}

.btn-icon.btn-danger {
    background: transparent;
}

.btn-icon.btn-danger:hover:not(:disabled) {
    background: rgba(255, 68, 85, 0.15);
}

.btn-link {
    background: transparent;
    color: var(--accent-primary);
    padding: var(--space-xs);
}

.btn-link:hover {
    text-decoration: underline;
}

/* Study Rating Buttons */
.rating-buttons {
    display: flex;
    gap: var(--space-sm);
    justify-content: center;
}

.btn-again, .btn-hard, .btn-good, .btn-easy {
    flex-direction: column;
    padding: var(--space-md) var(--space-lg);
    min-width: 90px;
}

.btn-again {
    background: rgba(255, 68, 85, 0.15);
    color: var(--accent-danger);
    border: 1px solid rgba(255, 68, 85, 0.3);
}

.btn-again:hover {
    background: rgba(255, 68, 85, 0.25);
}

.btn-hard {
    background: rgba(255, 170, 0, 0.15);
    color: var(--accent-warning);
    border: 1px solid rgba(255, 170, 0, 0.3);
}

.btn-hard:hover {
    background: rgba(255, 170, 0, 0.25);
}

.btn-good {
    background: rgba(0, 170, 255, 0.15);
    color: var(--accent-tertiary);
    border: 1px solid rgba(0, 170, 255, 0.3);
}

.btn-good:hover {
    background: rgba(0, 170, 255, 0.25);
}

.btn-easy {
    background: rgba(0, 255, 170, 0.15);
    color: var(--accent-primary);
    border: 1px solid rgba(0, 255, 170, 0.3);
}

.btn-easy:hover {
    background: rgba(0, 255, 170, 0.25);
}

.btn-label {
    font-weight: 600;
    font-size: 1rem;
}

.btn-hint {
    font-size: 0.75rem;
    opacity: 0.7;
    font-family: var(--font-mono);
}

.btn-show-answer {
    background: var(--gradient-primary);
    color: var(--bg-primary);
    padding: var(--space-md) var(--space-2xl);
    font-size: 1.1rem;
    font-weight: 600;
    box-shadow: var(--shadow-glow);
}

.btn-show-answer:hover {
    transform: translateY(-2px);
    box-shadow: 0 0 40px rgba(0, 255, 170, 0.4);
}

/* ============================================================================
   Cards & Deck Grid
   ============================================================================ */

.deck-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: var(--space-lg);
}

.deck-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    border: 1px solid rgba(255, 255, 255, 0.05);
    transition: all var(--transition-normal);
    display: flex;
    flex-direction: column;
}

.deck-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(0, 255, 170, 0.2);
}

.deck-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: var(--space-sm);
}

.deck-name {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
}

.deck-actions {
    display: flex;
    gap: var(--space-xs);
}

.deck-description {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: var(--space-md);
    flex: 1;
}

.deck-stats {
    display: flex;
    gap: var(--space-lg);
    padding: var(--space-md) 0;
    border-top: 1px solid rgba(255, 255, 255, 0.05);
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
    margin-bottom: var(--space-md);
}

.deck-stats .stat {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.deck-stats .stat-value {
    font-size: 1.5rem;
    font-weight: 700;
    font-family: var(--font-mono);
    color: var(--text-primary);
}

.deck-stats .stat-new .stat-value {
    color: var(--accent-tertiary);
}

.deck-stats .stat-due .stat-value {
    color: var(--accent-warning);
}

.deck-stats .stat-label {
    font-size: 0.75rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 1px;
}

.deck-footer {
    display: flex;
    gap: var(--space-sm);
    margin-top: auto;
}

.deck-footer .btn {
    flex: 1;
}

/* ============================================================================
   Flashcard Components
   ============================================================================ */

.flashcard-item {
    background: var(--bg-card);
    border-radius: var(--radius-md);
    padding: var(--space-lg);
    border: 1px solid rgba(255, 255, 255, 0.05);
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: var(--space-md);
    margin-bottom: var(--space-md);
}

.flashcard-content {
    flex: 1;
}

.flashcard-front, .flashcard-back {
    margin-bottom: var(--space-sm);
}

.flashcard-front .label, .flashcard-back .label {
    display: inline-block;
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--text-muted);
    margin-bottom: var(--space-xs);
}

.flashcard-front .label {
    color: var(--accent-primary);
}

.flashcard-back .label {
    color: var(--accent-secondary);
}

.flashcard-front p, .flashcard-back p {
    color: var(--text-primary);
}

.flashcard-actions {
    display: flex;
    gap: var(--space-xs);
}

.cards-list {
    display: flex;
    flex-direction: column;
}

/* ============================================================================
   Study Card (Interactive)
   ============================================================================ */

.study-container {
    max-width: 700px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.study-progress {
    width: 100%;
    margin-bottom: var(--space-lg);
}

.progress-text {
    display: block;
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: var(--space-sm);
}

.progress-bar {
    width: 100%;
    height: 6px;
    background: var(--bg-tertiary);
    border-radius: 3px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--gradient-primary);
    transition: width var(--transition-normal);
}

.study-deck-name {
    color: var(--text-muted);
    font-size: 0.85rem;
    margin-bottom: var(--space-md);
}

.study-card {
    width: 100%;
    height: 400px;
    perspective: 1000px;
    margin-bottom: var(--space-xl);
}

.study-card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.6s;
    transform-style: preserve-3d;
}

.study-card.flipped .study-card-inner {
    transform: rotateY(180deg);
}

.study-card-front, .study-card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    background: var(--bg-card);
    border-radius: var(--radius-xl);
    border: 1px solid rgba(255, 255, 255, 0.08);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-xl);
}

.study-card-front {
    box-shadow: var(--shadow-glow);
}

.study-card-back {
    transform: rotateY(180deg);
    box-shadow: var(--shadow-glow-pink);
    border-color: rgba(255, 0, 170, 0.2);
}

.card-content {
    text-align: center;
    width: 100%;
}

.card-text {
    font-size: 1.5rem;
    line-height: 1.5;
}

.card-question, .card-answer {
    margin-bottom: var(--space-lg);
}

.card-question .label, .card-answer .label {
    display: block;
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 2px;
    margin-bottom: var(--space-sm);
}

.card-question .label {
    color: var(--accent-primary);
}

.card-answer .label {
    color: var(--accent-secondary);
}

.card-question p {
    font-size: 1rem;
    color: var(--text-secondary);
}

.card-answer p {
    font-size: 1.3rem;
    color: var(--text-primary);
}

.study-actions {
    margin-bottom: var(--space-md);
}

.study-shortcuts {
    text-align: center;
}

.shortcut-hint {
    font-size: 0.8rem;
    color: var(--text-muted);
    font-family: var(--font-mono);
}

/* Study Complete */
.study-complete {
    text-align: center;
    padding: var(--space-2xl);
}

.complete-icon {
    font-size: 5rem;
    margin-bottom: var(--space-lg);
    animation: bounce 0.6s ease;
}

@keyframes bounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-20px); }
}

.complete-title {
    font-size: 2.5rem;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--space-md);
}

.complete-message {
    color: var(--text-secondary);
    font-size: 1.1rem;
    margin-bottom: var(--space-xl);
}

.complete-stats {
    display: flex;
    justify-content: center;
    gap: var(--space-xl);
    margin-bottom: var(--space-xl);
}

.complete-stats .stat {
    text-align: center;
}

.complete-stats .stat-value {
    font-size: 3rem;
    font-weight: 700;
    font-family: var(--font-mono);
    color: var(--accent-primary);
}

.complete-stats .stat-label {
    color: var(--text-muted);
    font-size: 0.85rem;
}

.complete-actions {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
}

/* ============================================================================
   Statistics Panel
   ============================================================================ */

.stats-panel {
    max-width: 900px;
    margin: 0 auto;
}

.stats-header {
    margin-bottom: var(--space-xl);
}

.stats-header h2 {
    font-size: 1.5rem;
    color: var(--text-primary);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
    gap: var(--space-md);
    margin-bottom: var(--space-xl);
}

.stat-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    text-align: center;
    border: 1px solid rgba(255, 255, 255, 0.05);
    transition: all var(--transition-normal);
}

.stat-card:hover {
    transform: translateY(-2px);
    border-color: rgba(255, 255, 255, 0.1);
}

.stat-card .stat-icon {
    font-size: 2rem;
    margin-bottom: var(--space-sm);
}

.stat-card .stat-value {
    font-size: 2rem;
    font-weight: 700;
    font-family: var(--font-mono);
    margin-bottom: var(--space-xs);
}

.stat-card .stat-label {
    font-size: 0.8rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 1px;
}

.stat-streak .stat-value { color: var(--accent-warning); }
.stat-today .stat-value { color: var(--accent-tertiary); }
.stat-correct .stat-value { color: var(--accent-primary); }
.stat-retention .stat-value { color: var(--accent-secondary); }
.stat-total .stat-value { color: var(--text-primary); }
.stat-learned .stat-value { color: var(--accent-tertiary); }

.stats-chart {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.stats-chart h3 {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: var(--space-lg);
}

.chart-bars {
    display: flex;
    align-items: flex-end;
    gap: var(--space-md);
    height: 120px;
}

.chart-bar-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.chart-bar {
    width: 100%;
    max-width: 40px;
    background: var(--gradient-primary);
    border-radius: var(--radius-sm) var(--radius-sm) 0 0;
    min-height: 4px;
    transition: height var(--transition-normal);
}

.chart-label {
    margin-top: var(--space-sm);
    font-size: 0.75rem;
    color: var(--text-muted);
    font-family: var(--font-mono);
}

/* Mini Stats */
.mini-stats {
    display: flex;
    gap: var(--space-lg);
    padding: var(--space-md);
    background: var(--bg-card);
    border-radius: var(--radius-md);
}

.mini-stat {
    text-align: center;
}

.mini-value {
    font-weight: 600;
    font-family: var(--font-mono);
}

.mini-label {
    font-size: 0.7rem;
    color: var(--text-muted);
    text-transform: uppercase;
}

/* ============================================================================
   Forms
   ============================================================================ */

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

.form-group label {
    display: block;
    font-weight: 500;
    margin-bottom: var(--space-sm);
    color: var(--text-primary);
}

.form-input {
    width: 100%;
    padding: var(--space-md);
    background: var(--bg-tertiary);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-family: var(--font-primary);
    font-size: 1rem;
    transition: all var(--transition-fast);
}

.form-input:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(0, 255, 170, 0.1);
}

.form-input::placeholder {
    color: var(--text-muted);
}

textarea.form-input {
    resize: vertical;
    min-height: 100px;
}

.form-select {
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='%23a0a0b0' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right var(--space-md) center;
    background-size: 1rem;
    padding-right: 2.5rem;
}

.form-hint {
    display: block;
    margin-top: var(--space-xs);
    font-size: 0.8rem;
    color: var(--text-muted);
}

.form-checkbox {
    display: flex;
    flex-direction: column;
}

.form-checkbox label {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    cursor: pointer;
}

.form-checkbox input[type="checkbox"] {
    width: 20px;
    height: 20px;
    accent-color: var(--accent-primary);
}

.form-actions {
    display: flex;
    gap: var(--space-md);
    justify-content: flex-end;
    margin-top: var(--space-xl);
}

.form-title {
    font-size: 1.5rem;
    margin-bottom: var(--space-lg);
    color: var(--text-primary);
}

/* Settings specific */
.settings-form {
    max-width: 600px;
}

.settings-section {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: var(--space-xl);
    margin-bottom: var(--space-lg);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.settings-section h2 {
    font-size: 1.1rem;
    color: var(--accent-primary);
    margin-bottom: var(--space-lg);
    padding-bottom: var(--space-md);
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

/* ============================================================================
   Modals
   ============================================================================ */

.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.8);
    backdrop-filter: blur(4px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 2000;
    animation: fadeIn 0.2s ease;
}

.modal-content {
    background: var(--bg-secondary);
    border-radius: var(--radius-xl);
    padding: var(--space-xl);
    max-width: 500px;
    width: 90%;
    max-height: 90vh;
    overflow-y: auto;
    position: relative;
    border: 1px solid rgba(255, 255, 255, 0.1);
    box-shadow: var(--shadow-lg);
    animation: slideUp 0.3s ease;
}

@keyframes slideUp {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

.modal-close {
    position: absolute;
    top: var(--space-md);
    right: var(--space-md);
    width: 36px;
    height: 36px;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-size: 1.5rem;
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.modal-close:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
}

.confirm-dialog {
    text-align: center;
    padding: var(--space-2xl);
}

.confirm-title {
    font-size: 1.3rem;
    margin-bottom: var(--space-md);
    color: var(--accent-danger);
}

.confirm-message {
    color: var(--text-secondary);
    margin-bottom: var(--space-xl);
}

.confirm-actions {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
}

/* ============================================================================
   Loading & Empty States
   ============================================================================ */

.loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--space-2xl);
}

.spinner {
    width: 48px;
    height: 48px;
    border: 3px solid var(--bg-tertiary);
    border-top-color: var(--accent-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: var(--space-md);
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.loading p {
    color: var(--text-secondary);
}

.empty-state {
    text-align: center;
    padding: var(--space-2xl);
}

.empty-icon {
    font-size: 4rem;
    margin-bottom: var(--space-lg);
    opacity: 0.5;
}

.empty-state h2, .empty-state h3 {
    font-size: 1.5rem;
    margin-bottom: var(--space-sm);
    color: var(--text-primary);
}

.empty-state p {
    color: var(--text-secondary);
    margin-bottom: var(--space-lg);
}

.study-empty {
    max-width: 500px;
    margin: var(--space-2xl) auto;
}

.empty-actions {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* ============================================================================
   Cram Mode Styles
   ============================================================================ */

.study-mode-toggle {
    display: flex;
    justify-content: center;
    gap: var(--space-sm);
    margin-bottom: var(--space-lg);
    padding: var(--space-sm);
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    width: fit-content;
    margin-left: auto;
    margin-right: auto;
}

.btn-mode {
    padding: var(--space-sm) var(--space-lg);
    background: transparent;
    color: var(--text-secondary);
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

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

.btn-mode.active {
    background: var(--gradient-primary);
    color: var(--bg-primary);
    font-weight: 600;
}

.btn-mode.active.cram {
    background: linear-gradient(135deg, #ff6b35, #ff4444);
    box-shadow: 0 0 20px rgba(255, 107, 53, 0.3);
}

.cram-banner {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-md);
    padding: var(--space-md) var(--space-lg);
    background: linear-gradient(135deg, rgba(255, 107, 53, 0.2), rgba(255, 68, 68, 0.2));
    border: 1px solid rgba(255, 107, 53, 0.3);
    border-radius: var(--radius-md);
    margin-bottom: var(--space-lg);
    color: #ff6b35;
    font-weight: 500;
    animation: pulse-cram 2s ease-in-out infinite;
}

@keyframes pulse-cram {
    0%, 100% { box-shadow: 0 0 10px rgba(255, 107, 53, 0.2); }
    50% { box-shadow: 0 0 20px rgba(255, 107, 53, 0.4); }
}

.cram-icon {
    font-size: 1.5rem;
    animation: flame 0.5s ease-in-out infinite alternate;
}

@keyframes flame {
    from { transform: scale(1); }
    to { transform: scale(1.1); }
}

.cram-stats {
    margin-left: auto;
    font-family: var(--font-mono);
    color: var(--text-secondary);
}

.cram-continue {
    background: linear-gradient(135deg, #ff6b35, #ff4444) !important;
    animation: pulse-button 1.5s ease-in-out infinite;
}

@keyframes pulse-button {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.02); }
}

/* ============================================================================
   Banners & Alerts
   ============================================================================ */

.error-banner, .success-banner {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--space-md) var(--space-lg);
    border-radius: var(--radius-md);
    margin-bottom: var(--space-lg);
    animation: slideDown 0.3s ease;
}

@keyframes slideDown {
    from { opacity: 0; transform: translateY(-10px); }
    to { opacity: 1; transform: translateY(0); }
}

.error-banner {
    background: rgba(255, 68, 85, 0.15);
    border: 1px solid rgba(255, 68, 85, 0.3);
    color: var(--accent-danger);
}

.success-banner {
    background: rgba(0, 255, 170, 0.15);
    border: 1px solid rgba(0, 255, 170, 0.3);
    color: var(--accent-primary);
}

.error-banner button, .success-banner button {
    background: transparent;
    border: none;
    color: inherit;
    font-size: 1.2rem;
    cursor: pointer;
    padding: var(--space-xs);
    opacity: 0.7;
    transition: opacity var(--transition-fast);
}

.error-banner button:hover, .success-banner button:hover {
    opacity: 1;
}

/* ============================================================================
   Responsive Design
   ============================================================================ */

@media (max-width: 768px) {
    .main-content {
        padding: var(--space-md);
        padding-top: calc(70px + var(--space-md));
    }
    
    .navbar {
        padding: 0 var(--space-md);
    }
    
    .nav-text {
        display: none;
    }
    
    .navbar-menu {
        gap: var(--space-xs);
    }
    
    .nav-link {
        padding: var(--space-sm);
    }
    
    .nav-icon {
        font-size: 1.4rem;
    }
    
    .page-header {
    flex-direction: column;
        align-items: stretch;
        gap: var(--space-md);
    }
    
    .page-header h1 {
        font-size: 1.5rem;
    }
    
    .deck-grid {
        grid-template-columns: 1fr;
    }
    
    .deck-stats {
        justify-content: space-around;
    }
    
    .rating-buttons {
        flex-wrap: wrap;
    }
    
    .btn-again, .btn-hard, .btn-good, .btn-easy {
        min-width: 80px;
        padding: var(--space-sm) var(--space-md);
    }
    
    .study-card {
        height: 300px;
    }
    
    .card-text {
        font-size: 1.2rem;
    }
    
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .modal-content {
        padding: var(--space-lg);
        width: 95%;
    }
    
    .form-actions {
        flex-direction: column;
    }
    
    .form-actions .btn {
        width: 100%;
    }
}

@media (max-width: 480px) {
    html {
        font-size: 14px;
    }
    
    .logo-text {
        display: none;
    }
    
    .header-back {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .header-actions {
        width: 100%;
    }
    
    .header-actions .btn {
        flex: 1;
    }
    
    .complete-stats .stat-value {
        font-size: 2rem;
    }
}

/* ============================================================================
   Authentication Pages
   ============================================================================ */

/* Loading screen */
.loading-screen {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    background: var(--gradient-bg);
    gap: var(--space-lg);
}

.loading-spinner {
    width: 50px;
    height: 50px;
    border: 3px solid var(--bg-tertiary);
    border-top-color: var(--accent-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Auth page layout */
.auth-page {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-xl);
    background: var(--gradient-bg);
    background-attachment: fixed;
}

.auth-container {
    width: 100%;
    max-width: 420px;
    animation: fadeInUp 0.5s ease;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Auth header */
.auth-header {
    text-align: center;
    margin-bottom: var(--space-2xl);
}

.auth-title {
    font-size: 3rem;
    font-weight: 800;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--space-sm);
}

.auth-subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Auth form */
.auth-form {
    background: var(--bg-card);
    border: 1px solid rgba(255, 255, 255, 0.05);
    border-radius: var(--radius-lg);
    padding: var(--space-2xl);
    box-shadow: var(--shadow-lg);
}

.form-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: var(--space-xl);
    text-align: center;
    color: var(--text-primary);
}

.auth-error {
    background: rgba(255, 68, 85, 0.1);
    border: 1px solid var(--accent-danger);
    color: var(--accent-danger);
    padding: var(--space-md);
    border-radius: var(--radius-md);
    margin-bottom: var(--space-lg);
    font-size: 0.9rem;
    text-align: center;
}

.auth-form .form-group {
    margin-bottom: var(--space-lg);
}

.auth-form label {
    display: block;
    font-weight: 600;
    margin-bottom: var(--space-sm);
    color: var(--text-primary);
    font-size: 0.95rem;
}

.auth-form label .required {
    color: var(--accent-danger);
}

.auth-form label .optional {
    color: var(--text-muted);
    font-weight: 400;
    font-size: 0.85rem;
}

.auth-form input {
    width: 100%;
    padding: var(--space-md) var(--space-lg);
    background: var(--bg-secondary);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 1rem;
    font-family: var(--font-primary);
    transition: var(--transition-fast);
}

.auth-form input:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(0, 255, 170, 0.1);
}

.auth-form input::placeholder {
    color: var(--text-muted);
}

.auth-form input:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

/* Auth button */
.auth-button {
    width: 100%;
    padding: var(--space-md) var(--space-xl);
    background: var(--gradient-primary);
    border: none;
    border-radius: var(--radius-md);
    color: var(--bg-primary);
    font-size: 1rem;
    font-weight: 700;
    font-family: var(--font-primary);
    cursor: pointer;
    transition: var(--transition-normal);
    margin-top: var(--space-md);
}

.auth-button:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: var(--shadow-glow);
}

.auth-button:active:not(:disabled) {
    transform: translateY(0);
}

.auth-button:disabled {
    opacity: 0.7;
    cursor: not-allowed;
}

/* Auth footer */
.auth-footer {
    text-align: center;
    margin-top: var(--space-xl);
    color: var(--text-secondary);
}

.auth-link {
    color: var(--accent-primary);
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition-fast);
}

.auth-link:hover {
    text-decoration: underline;
}

/* Navbar user section */
.navbar-user {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.user-greeting {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.logout-btn {
    padding: var(--space-sm) var(--space-md);
    background: transparent;
    border: 1px solid var(--accent-danger);
    border-radius: var(--radius-sm);
    color: var(--accent-danger);
    font-size: 0.85rem;
    font-weight: 600;
    font-family: var(--font-primary);
    cursor: pointer;
    transition: var(--transition-fast);
}

.logout-btn:hover {
    background: var(--accent-danger);
    color: white;
}

/* Responsive auth */
@media (max-width: 480px) {
    .auth-container {
        max-width: 100%;
    }
    
    .auth-title {
        font-size: 2.5rem;
    }
    
    .auth-form {
        padding: var(--space-xl);
    }
    
    .navbar-user {
        flex-direction: column;
        gap: var(--space-xs);
    }
    
    .user-greeting {
        display: none;
    }
}