/* CSS Variables */
:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary-color: #06b6d4;
    --success-color: #10b981;
    --error-color: #ef4444;
    --warning-color: #f59e0b;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --border-color: #e5e7eb;
    --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 0.3s ease;
}

/* Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    overflow-x: hidden;
}

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

/* Header Styles */
.header {
    background: var(--bg-primary);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    margin-bottom: 2rem;
    box-shadow: var(--shadow-lg);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.header-content {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1rem;
}

.header-content i {
    font-size: 2.5rem;
    color: var(--primary-color);
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.header-text h1 {
    font-size: 1.875rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

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

/* Progress Bar */
.progress-container {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.progress-bar {
    flex: 1;
    height: 0.5rem;
    background: var(--bg-tertiary);
    border-radius: 9999px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    border-radius: 9999px;
    width: 0%;
    transition: var(--transition);
}

.progress-text {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    white-space: nowrap;
}

/* Main Content */
.main-content {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* Welcome Screen */
.welcome-screen {
    background: var(--bg-primary);
    border-radius: var(--border-radius);
    padding: 3rem;
    box-shadow: var(--shadow-lg);
    text-align: center;
    max-width: 600px;
    width: 100%;
}

.welcome-content .welcome-icon {
    font-size: 4rem;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.welcome-content h2 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.welcome-content > p {
    color: var(--text-secondary);
    margin-bottom: 2rem;
    font-size: 1.125rem;
}

.topic-list {
    list-style: none;
    margin-bottom: 2rem;
    text-align: left;
}

.topic-list li {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem 0;
    font-size: 1rem;
}

.topic-list i {
    color: var(--success-color);
    font-size: 1rem;
}

.quiz-info {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
    padding: 1.5rem;
    background: var(--bg-secondary);
    border-radius: var(--border-radius);
}

.info-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.info-item i {
    color: var(--primary-color);
}

.start-btn {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    border: none;
    padding: 1rem 2rem;
    border-radius: var(--border-radius);
    font-size: 1.125rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-md);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.start-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

/* Quiz Container */
.quiz-container {
    width: 100%;
    max-width: 800px;
}

.question-card {
    background: var(--bg-primary);
    border-radius: var(--border-radius);
    padding: 2rem;
    box-shadow: var(--shadow-lg);
}

.question-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 2px solid var(--bg-tertiary);
}

.question-number {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--primary-color);
}

.score-display {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.score-display i {
    color: var(--warning-color);
}

.question-content {
    margin-bottom: 2rem;
}

.question-text {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    line-height: 1.6;
    color: var(--text-primary);
}

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

.option {
    display: flex;
    align-items: flex-start;
    gap: 1rem;
    padding: 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transition);
    background: var(--bg-primary);
}

.option:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
    transform: translateY(-1px);
}

.option.selected {
    border-color: var(--primary-color);
    background: rgba(37, 99, 235, 0.05);
}

.option.correct {
    border-color: var(--success-color);
    background: rgba(16, 185, 129, 0.1);
}

.option.incorrect {
    border-color: var(--error-color);
    background: rgba(239, 68, 68, 0.1);
}

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

.option-letter {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 2rem;
    height: 2rem;
    background: var(--bg-tertiary);
    border-radius: 50%;
    font-weight: 600;
    font-size: 0.875rem;
    color: var(--text-primary);
    flex-shrink: 0;
    transition: var(--transition);
}

.option.selected .option-letter {
    background: var(--primary-color);
    color: white;
}

.option.correct .option-letter {
    background: var(--success-color);
    color: white;
}

.option.incorrect .option-letter {
    background: var(--error-color);
    color: white;
}

.option-text {
    flex: 1;
    font-size: 1rem;
    line-height: 1.5;
    color: var(--text-primary);
}

/* Feedback Container */
.feedback-container {
    margin-top: 1.5rem;
    padding: 1.25rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    animation: slideIn 0.3s ease-out;
}

.feedback-container.correct {
    background: rgba(16, 185, 129, 0.1);
    border: 1px solid var(--success-color);
}

.feedback-container.incorrect {
    background: rgba(239, 68, 68, 0.1);
    border: 1px solid var(--error-color);
}

.feedback-content {
    display: flex;
    align-items: flex-start;
    gap: 1rem;
}

.feedback-icon {
    font-size: 1.5rem;
    flex-shrink: 0;
}

.feedback-icon.correct {
    color: var(--success-color);
}

.feedback-icon.incorrect {
    color: var(--error-color);
}

.feedback-text {
    flex: 1;
}

.feedback-text h4 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.feedback-text.correct h4 {
    color: var(--success-color);
}

.feedback-text.incorrect h4 {
    color: var(--error-color);
}

.feedback-text p {
    color: var(--text-secondary);
    font-size: 0.875rem;
    line-height: 1.5;
}

/* Question Actions */
.question-actions {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
}

.nav-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border: 2px solid var(--border-color);
    background: var(--bg-primary);
    color: var(--text-primary);
    border-radius: var(--border-radius);
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.nav-btn:hover:not(:disabled) {
    border-color: var(--primary-color);
    color: var(--primary-color);
    transform: translateY(-1px);
}

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

.next-btn:not(:disabled) {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

.next-btn:not(:disabled):hover {
    background: var(--primary-dark);
    border-color: var(--primary-dark);
    color: white;
}

/* Results Screen */
.results-screen {
    background: var(--bg-primary);
    border-radius: var(--border-radius);
    padding: 3rem;
    box-shadow: var(--shadow-lg);
    text-align: center;
    max-width: 600px;
    width: 100%;
}

.results-header {
    margin-bottom: 2rem;
}

.results-icon {
    font-size: 4rem;
    margin-bottom: 1rem;
    background: linear-gradient(135deg, var(--warning-color), #f97316);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.results-icon.excellent {
    background: linear-gradient(135deg, var(--success-color), #059669);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.results-icon.good {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.results-header h2 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
}

.score-summary {
    margin-bottom: 2rem;
    padding: 2rem;
    background: var(--bg-secondary);
    border-radius: var(--border-radius);
}

.final-score {
    font-size: 3rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.score-percentage {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.performance-analysis {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-bottom: 2rem;
}

.analysis-item {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 1rem;
    border-radius: var(--border-radius);
    background: var(--bg-secondary);
    font-weight: 500;
}

.analysis-item i.correct {
    color: var(--success-color);
}

.analysis-item i.incorrect {
    color: var(--error-color);
}

.results-actions {
    display: flex;
    gap: 1rem;
    justify-content: center;
}

.action-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 1rem 1.5rem;
    border: 2px solid var(--border-color);
    background: var(--bg-primary);
    color: var(--text-primary);
    border-radius: var(--border-radius);
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
}

.action-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    transform: translateY(-1px);
}

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

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

/* Sound Toggle */
.sound-toggle {
    position: fixed;
    top: 1rem;
    right: 1rem;
    width: 3rem;
    height: 3rem;
    background: var(--bg-primary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-md);
    z-index: 1000;
}

.sound-toggle:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-lg);
}

.sound-toggle i {
    color: var(--primary-color);
    font-size: 1.25rem;
}

.sound-toggle.muted i {
    color: var(--text-secondary);
}

/* Animations */
@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(1rem);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

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

@keyframes pulse {
    0%, 100% {
        transform: scale(1);
    }
    50% {
        transform: scale(1.05);
    }
}

.pulse {
    animation: pulse 0.5s ease-in-out;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 0.5rem;
    }
    
    .header {
        padding: 1rem;
    }
    
    .header-content {
        flex-direction: column;
        text-align: center;
        gap: 0.5rem;
    }
    
    .header-text h1 {
        font-size: 1.5rem;
    }
    
    .progress-container {
        flex-direction: column;
        gap: 0.5rem;
    }
    
    .welcome-screen,
    .results-screen {
        padding: 2rem 1rem;
    }
    
    .welcome-content h2 {
        font-size: 1.5rem;
    }
    
    .question-card {
        padding: 1.5rem;
    }
    
    .question-header {
        flex-direction: column;
        gap: 1rem;
        align-items: flex-start;
    }
    
    .question-text {
        font-size: 1.125rem;
    }
    
    .question-actions {
        flex-direction: column;
    }
    
    .quiz-info {
        grid-template-columns: 1fr;
    }
    
    .results-actions {
        flex-direction: column;
    }
    
    .performance-analysis {
        grid-template-columns: 1fr;
    }
    
    .final-score {
        font-size: 2rem;
    }
    
    .score-percentage {
        font-size: 1.25rem;
    }
}

@media (max-width: 480px) {
    .option {
        padding: 0.75rem;
    }
    
    .option-letter {
        width: 1.5rem;
        height: 1.5rem;
        font-size: 0.75rem;
    }
    
    .option-text {
        font-size: 0.875rem;
    }
    
    .nav-btn {
        padding: 0.5rem 1rem;
        font-size: 0.875rem;
    }
}