/* CS Flashcards Styles */

:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b;
    --success-color: #059669;
    --warning-color: #d97706;
    --danger-color: #dc2626;
    --background-color: #f8fafc;
    --card-background: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --border-radius: 0.5rem;
    --transition: all 0.2s ease-in-out;
}

/* Base Styles */
* {
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--background-color);
    color: var(--text-primary);
    margin: 0;
    padding: 0;
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem;
    min-height: 100vh;
}

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

.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--border-radius);
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
    background: transparent;
}

.btn:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn:active {
    transform: translateY(0);
}

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

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

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

.btn-secondary:hover {
    background-color: #475569;
}

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

.btn-warning:hover {
    background-color: #b45309;
}

.btn-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    padding: 0.25rem;
    color: var(--text-secondary);
}

/* Header */
.header {
    background: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    margin-bottom: 2rem;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem;
}

.title {
    font-size: 1.875rem;
    font-weight: 700;
    margin: 0;
    color: var(--primary-color);
}

.header-controls {
    display: flex;
    gap: 0.75rem;
}

/* Session Setup */
.session-setup {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 60vh;
}

.setup-card {
    background: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    padding: 2rem;
    width: 100%;
    max-width: 600px;
}

.setup-card h2 {
    text-align: center;
    margin-bottom: 2rem;
    color: var(--primary-color);
}

.setup-section {
    margin-bottom: 2rem;
}

.setup-section h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
    font-size: 1.125rem;
}

.filter-group {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
}

.filter-option {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1rem;
    background: var(--background-color);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transition);
    user-select: none;
}

.filter-option:hover {
    border-color: var(--primary-color);
    background: #eff6ff;
}

.filter-option input[type="checkbox"]:checked + span,
.filter-option input[type="radio"]:checked + span {
    color: var(--primary-color);
    font-weight: 600;
}

.filter-option input[type="checkbox"]:checked,
.filter-option input[type="radio"]:checked {
    accent-color: var(--primary-color);
}

.setup-actions {
    text-align: center;
    margin-top: 2rem;
}

/* Flashcard Interface */
.flashcard-interface {
    max-width: 800px;
    margin: 0 auto;
}

/* Progress Bar */
.progress-container {
    margin-bottom: 2rem;
}

.progress-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.5rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.progress-bar {
    height: 0.5rem;
    background: var(--border-color);
    border-radius: 0.25rem;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--success-color));
    transition: width 0.3s ease;
    width: 0%;
}

/* Flashcard */
.flashcard-container {
    perspective: 1200px;
    margin-bottom: 2rem;
    position: relative;
}

.flashcard {
    position: relative;
    width: 100%;
    min-height: 500px;
    transform-style: preserve-3d;
    transition: transform 0.6s cubic-bezier(0.4, 0.0, 0.2, 1);
    cursor: pointer;
}

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

.flashcard.revealing {
    transform: scale(1.02);
}

.flashcard.touch-active {
    transform: scale(0.98);
    transition: transform 0.1s ease;
}

.flashcard-front,
.flashcard-back {
    position: absolute;
    width: 100%;
    min-height: 500px;
    background: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    backface-visibility: hidden;
    display: flex;
    flex-direction: column;
    border: 2px solid transparent;
    transition: border-color 0.3s ease, box-shadow 0.3s ease;
}

.flashcard:hover .flashcard-front,
.flashcard:hover .flashcard-back {
    border-color: var(--primary-color);
    box-shadow: 0 8px 25px rgba(37, 99, 235, 0.15);
}

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

.flashcard-back.slide-in {
    animation: slideInFromRight 0.3s ease-out;
}

/* Enhanced animations */
.flashcard.fade-in {
    animation: cardFadeIn 0.4s ease-out;
}

.flashcard.fade-out {
    animation: cardFadeOut 0.2s ease-in;
}

@keyframes cardFadeIn {
    from {
        opacity: 0;
        transform: translateY(20px) scale(0.95);
    }
    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

@keyframes cardFadeOut {
    from {
        opacity: 1;
        transform: scale(1);
    }
    to {
        opacity: 0;
        transform: scale(0.95);
    }
}

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

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 1.5rem 0;
}

.topic-badge {
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.75rem;
    font-weight: 600;
}

.frequency-badge {
    background: var(--warning-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.75rem;
    font-weight: 600;
}

.card-content {
    flex: 1;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    justify-content: center;
}

.question-content {
    font-size: 1.25rem;
    line-height: 1.6;
    text-align: center;
    color: var(--text-primary);
}

.question-summary {
    margin-bottom: 1.5rem;
    padding: 1rem;
    background: var(--background-color);
    border-radius: var(--border-radius);
}

.question-text {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-top: 0.5rem;
}

.answer-content {
    margin-bottom: 1.5rem;
}

.answer-text {
    font-size: 1rem;
    line-height: 1.6;
    margin-top: 0.5rem;
    white-space: pre-line;
}

.exam-info {
    padding: 1rem;
    background: #f0f9ff;
    border-left: 4px solid var(--primary-color);
    border-radius: 0 var(--border-radius) var(--border-radius) 0;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.card-footer {
    padding: 1.5rem;
    border-top: 1px solid var(--border-color);
}

.card-footer .btn {
    width: 100%;
    justify-content: center;
}

/* Difficulty Buttons */
.difficulty-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.75rem;
}

.btn-difficulty {
    flex-direction: column;
    padding: 1rem 0.5rem;
    font-size: 0.875rem;
    text-align: center;
}

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

.btn-again:hover {
    background-color: #b91c1c;
}

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

.btn-hard:hover {
    background-color: #b45309;
}

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

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

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

.btn-easy:hover {
    background-color: #047857;
}

.keyboard-hint {
    font-size: 0.75rem;
    opacity: 0.8;
    margin-top: 0.25rem;
}

/* Session Controls */
.session-controls {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

/* Session Complete */
.session-complete {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 60vh;
}

.complete-card {
    background: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    padding: 2rem;
    width: 100%;
    max-width: 500px;
    text-align: center;
}

.complete-header h2 {
    color: var(--success-color);
    margin-bottom: 2rem;
}

.complete-stats {
    margin-bottom: 2rem;
}

.stat-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 0;
    border-bottom: 1px solid var(--border-color);
}

.stat-item:last-child {
    border-bottom: none;
}

.stat-label {
    color: var(--text-secondary);
}

.stat-value {
    font-weight: 600;
    color: var(--text-primary);
}

.complete-actions {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

/* Loading Overlay */
.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.loading-spinner {
    width: 3rem;
    height: 3rem;
    border: 4px solid var(--border-color);
    border-top: 4px solid var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

.loading-text {
    color: white;
    margin-top: 1rem;
    font-size: 1.125rem;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Modal Styles */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.modal-content {
    background: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    width: 90%;
    max-width: 500px;
    max-height: 80vh;
    overflow-y: auto;
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.modal-header h3 {
    margin: 0;
    color: var(--text-primary);
}

.modal-body {
    padding: 1.5rem;
}

.modal-footer {
    padding: 1.5rem;
    border-top: 1px solid var(--border-color);
    text-align: right;
}

.setting-group {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    padding: 0.75rem 0;
    border-bottom: 1px solid var(--border-color);
}

.setting-group:last-child {
    border-bottom: none;
    margin-bottom: 0;
}

.setting-group label {
    color: var(--text-primary);
    font-weight: 500;
}

.setting-group input,
.setting-group select {
    padding: 0.5rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    background: var(--card-background);
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 0.5rem;
    }
    
    .header-content {
        flex-direction: column;
        gap: 1rem;
        text-align: center;
    }
    
    .header-controls {
        flex-wrap: wrap;
        justify-content: center;
        gap: 0.5rem;
    }
    
    .setup-card,
    .complete-card {
        padding: 1.5rem;
        margin: 0 0.5rem;
    }
    
    .filter-group {
        flex-direction: column;
        gap: 0.5rem;
    }
    
    .filter-option {
        width: 100%;
        padding: 1rem;
        font-size: 1rem;
    }
    
    .flashcard {
        min-height: 400px;
        margin: 0 0.5rem;
    }
    
    .flashcard-front,
    .flashcard-back {
        min-height: 400px;
        padding: 1rem;
    }
    
    .card-content {
        padding: 1rem;
    }
    
    .question-content {
        font-size: 1.125rem;
        line-height: 1.5;
    }
    
    .difficulty-buttons {
        grid-template-columns: repeat(2, 1fr);
        gap: 0.75rem;
    }
    
    .btn-difficulty {
        padding: 1rem 0.5rem;
        font-size: 0.875rem;
        min-height: 60px;
    }
    
    .session-controls {
        flex-direction: column;
        align-items: center;
        gap: 0.75rem;
        margin: 1rem 0.5rem;
    }
    
    .complete-actions {
        gap: 0.75rem;
    }
    
    .keyboard-hint {
        display: none;
    }
    
    .progress-info {
        font-size: 0.875rem;
        flex-direction: column;
        gap: 0.25rem;
        text-align: center;
    }
    
    .modal-content {
        margin: 1rem;
        max-height: calc(100vh - 2rem);
    }
    
    .setup-section h3 {
        font-size: 1rem;
        margin-bottom: 0.75rem;
    }
    
    .topic-badge,
    .frequency-badge {
        font-size: 0.75rem;
        padding: 0.25rem 0.5rem;
    }
}

@media (max-width: 480px) {
    .title {
        font-size: 1.5rem;
    }
    
    .btn {
        padding: 0.75rem 1rem;
        font-size: 0.875rem;
        min-height: 48px;
    }
    
    .question-content {
        font-size: 1rem;
        padding: 0.5rem;
    }
    
    .card-content {
        padding: 0.75rem;
    }
    
    .card-footer {
        padding: 0.75rem;
    }
    
    .btn-difficulty {
        padding: 0.75rem 0.25rem;
        font-size: 0.8rem;
        min-height: 56px;
    }
    
    .flashcard {
        min-height: 350px;
        margin: 0 0.25rem;
    }
    
    .flashcard-front,
    .flashcard-back {
        min-height: 350px;
    }
    
    .setup-card {
        padding: 1rem;
        margin: 0 0.25rem;
    }
    
    .complete-card {
        padding: 1rem;
        margin: 0 0.25rem;
    }
    
    .difficulty-buttons {
        gap: 0.5rem;
    }
    
    .progress-container {
        margin: 0 0.5rem 1rem;
    }
    
    .session-controls {
        margin: 1rem 0.25rem;
    }
}

/* Landscape orientation on mobile */
@media (max-width: 768px) and (orientation: landscape) {
    .flashcard {
        min-height: 300px;
    }
    
    .flashcard-front,
    .flashcard-back {
        min-height: 300px;
    }
    
    .question-content {
        font-size: 1rem;
    }
    
    .difficulty-buttons {
        grid-template-columns: repeat(4, 1fr);
        gap: 0.5rem;
    }
    
    .btn-difficulty {
        padding: 0.5rem 0.25rem;
        font-size: 0.75rem;
        min-height: 48px;
    }
}

/* Animation Classes */
.fade-in {
    animation: fadeIn 0.3s ease-in-out;
}

.fade-out {
    animation: fadeOut 0.3s ease-in-out;
}

.slide-in {
    animation: slideIn 0.3s ease-in-out;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes fadeOut {
    from { opacity: 1; }
    to { opacity: 0; }
}

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

@keyframes slideInRight {
    from { 
        transform: translateX(100%); 
        opacity: 0; 
    }
    to { 
        transform: translateX(0); 
        opacity: 1; 
    }
}

@keyframes slideOutRight {
    from { 
        transform: translateX(0); 
        opacity: 1; 
    }
    to { 
        transform: translateX(100%); 
        opacity: 0; 
    }
}

/* Error Notifications */
.error-notification {
    font-family: inherit;
    font-size: 0.875rem;
    line-height: 1.4;
}

/* Button States */
.btn.disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none !important;
}

.btn-difficulty.selected {
    transform: scale(0.95);
    box-shadow: inset 0 2px 4px rgba(0,0,0,0.2);
}

/* Custom Properties for Dynamic Animation Timing */
:root {
    --flip-duration: 0.6s;
}

.flashcard {
    transition: transform var(--flip-duration) cubic-bezier(0.4, 0.0, 0.2, 1);
}

/* Focus States for Accessibility */
.btn:focus,
.filter-option:focus-within,
input:focus,
select:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* High Contrast Mode Support */
@media (prefers-contrast: high) {
    :root {
        --border-color: #000000;
        --text-secondary: #000000;
    }
}

/* Reduced Motion Support */
@media (prefers-reduced-motion: reduce) {
    .flashcard {
        transition: none;
    }
    
    .loading-spinner {
        animation: none;
    }
    
    .btn:hover {
        transform: none;
    }
}