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

:root {
    --primary-color: #2ecc71;
    --secondary-color: #27ae60;
    --accent-color: #3498db;
    --danger-color: #e74c3c;
    --warning-color: #f39c12;
    --dark-color: #2c3e50;
    --light-color: #ecf0f1;
    --success-color: #27ae60;
    --text-color: #333;
    --border-radius: 12px;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.15);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
    color: var(--text-color);
}

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

header {
    text-align: center;
    color: white;
    margin-bottom: 30px;
    animation: fadeInDown 0.6s ease;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 10px;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.2);
}

header .subtitle {
    font-size: 1.1rem;
    opacity: 0.9;
}

/* Screen Management */
.screen {
    display: none;
    animation: fadeIn 0.5s ease;
}

.screen.active {
    display: block;
}

/* Welcome Card */
.welcome-card {
    background: white;
    border-radius: var(--border-radius);
    padding: 40px;
    box-shadow: var(--shadow-lg);
    text-align: center;
}

.welcome-card h2 {
    color: var(--dark-color);
    margin-bottom: 20px;
    font-size: 2rem;
}

.welcome-card > p {
    color: #666;
    line-height: 1.8;
    margin-bottom: 30px;
    font-size: 1.1rem;
}

/* Quiz Selector */
.quiz-selector {
    margin: 30px 0;
    padding: 30px;
    background: var(--light-color);
    border-radius: var(--border-radius);
}

.quiz-selector h3 {
    color: var(--dark-color);
    margin-bottom: 20px;
    font-size: 1.3rem;
}

.quiz-options {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 15px;
    margin-top: 20px;
}

.quiz-option-card {
    position: relative;
    display: block;
    cursor: pointer;
    transition: all 0.3s ease;
}

.quiz-option-card input[type="radio"] {
    position: absolute;
    opacity: 0;
    cursor: pointer;
}

.option-content {
    background: white;
    border: 3px solid #ddd;
    border-radius: var(--border-radius);
    padding: 20px;
    transition: all 0.3s ease;
    min-height: 140px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.quiz-option-card:hover .option-content {
    border-color: var(--accent-color);
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.quiz-option-card input[type="radio"]:checked + .option-content {
    border-color: var(--primary-color);
    background: #f0fdf4;
    box-shadow: var(--shadow-lg);
}

.option-icon {
    font-size: 3rem;
    margin-bottom: 15px;
}

.option-title {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--dark-color);
    margin-bottom: 8px;
}

.option-desc {
    font-size: 0.95rem;
    color: #666;
    text-align: center;
}

.info-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin: 30px 0;
}

.info-item {
    display: flex;
    align-items: center;
    gap: 15px;
    padding: 20px;
    background: var(--light-color);
    border-radius: var(--border-radius);
    transition: transform 0.3s ease;
}

.info-item:hover {
    transform: translateY(-5px);
}

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

.info-item strong {
    display: block;
    color: var(--dark-color);
    margin-bottom: 5px;
}

.info-item p {
    color: #666;
    font-size: 0.95rem;
}

/* Buttons */
.btn {
    padding: 15px 30px;
    border: none;
    border-radius: var(--border-radius);
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

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

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

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none !important;
}

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

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

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

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

/* Quiz Screen */
.quiz-header {
    background: white;
    border-radius: var(--border-radius);
    padding: 20px;
    margin-bottom: 20px;
    box-shadow: var(--shadow);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 20px;
}

.progress-container {
    flex: 1;
    min-width: 200px;
}

.progress-text {
    margin-bottom: 10px;
    font-weight: 600;
    color: var(--dark-color);
}

.progress-bar {
    height: 10px;
    background: var(--light-color);
    border-radius: 5px;
    overflow: hidden;
}

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

.timer-container {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--dark-color);
}

.timer-icon {
    font-size: 1.5rem;
}

/* Question Card */
.question-card {
    background: white;
    border-radius: var(--border-radius);
    padding: 40px;
    box-shadow: var(--shadow-lg);
    min-height: 400px;
}

.question-category {
    display: inline-block;
    padding: 8px 16px;
    background: var(--accent-color);
    color: white;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 600;
    margin-bottom: 20px;
}

.question-text {
    color: var(--dark-color);
    font-size: 1.5rem;
    line-height: 1.6;
    margin-bottom: 30px;
}

.options {
    display: flex;
    flex-direction: column;
    gap: 15px;
    margin-bottom: 30px;
}

.option {
    padding: 20px;
    background: var(--light-color);
    border: 2px solid transparent;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 1.1rem;
}

.option:hover {
    background: #dce4e8;
    border-color: var(--accent-color);
    transform: translateX(5px);
}

.option.selected {
    background: #d4edda;
    border-color: var(--primary-color);
    font-weight: 600;
}

.option.correct {
    background: #d4edda;
    border-color: var(--success-color);
}

.option.wrong {
    background: #f8d7da;
    border-color: var(--danger-color);
}

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

.option.disabled.correct {
    opacity: 1;
}

.option.disabled.wrong {
    opacity: 1;
}

.inline-explanation {
    margin-top: 20px;
    padding: 20px;
    background: #f8f9fa;
    border-radius: var(--border-radius);
    border-left: 4px solid var(--primary-color);
}

.answer-feedback {
    font-size: 1.1rem;
    font-weight: 700;
    margin-bottom: 10px;
}

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

.answer-feedback.wrong {
    color: var(--danger-color);
}

.explanation-text {
    color: #555;
    line-height: 1.6;
}

.navigation-buttons {
    display: flex;
    gap: 15px;
    justify-content: center;
}

/* Result Screen */
.result-card {
    background: white;
    border-radius: var(--border-radius);
    padding: 40px;
    box-shadow: var(--shadow-lg);
    text-align: center;
}

.result-card h2 {
    color: var(--dark-color);
    margin-bottom: 30px;
    font-size: 2rem;
}

.score-display {
    margin: 30px 0;
}

.score-circle {
    width: 200px;
    height: 200px;
    margin: 0 auto;
    position: relative;
}

.score-circle svg {
    transform: rotate(-90deg);
}

.score-bg {
    fill: none;
    stroke: var(--light-color);
    stroke-width: 8;
}

.score-progress {
    fill: none;
    stroke: var(--primary-color);
    stroke-width: 8;
    stroke-linecap: round;
    stroke-dasharray: 283;
    stroke-dashoffset: 283;
    transition: stroke-dashoffset 1s ease;
}

.score-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 3rem;
    font-weight: bold;
    color: var(--primary-color);
}

.score-label {
    font-size: 1.5rem;
}

.result-stats {
    display: flex;
    justify-content: space-around;
    margin: 30px 0;
    padding: 20px;
    background: var(--light-color);
    border-radius: var(--border-radius);
}

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

.stat-label {
    display: block;
    color: #666;
    margin-bottom: 10px;
    font-size: 0.9rem;
}

.stat-value {
    display: block;
    font-size: 2rem;
    font-weight: bold;
}

.stat-value.correct {
    color: var(--success-color);
}

.stat-value.wrong {
    color: var(--danger-color);
}

.performance-message {
    margin: 20px 0;
    padding: 20px;
    border-radius: var(--border-radius);
    font-size: 1.1rem;
    font-weight: 600;
}

.performance-message.excellent {
    background: #d4edda;
    color: #155724;
}

.performance-message.good {
    background: #cce5ff;
    color: #004085;
}

.performance-message.fair {
    background: #fff3cd;
    color: #856404;
}

.performance-message.poor {
    background: #f8d7da;
    color: #721c24;
}

.result-buttons {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin-top: 30px;
}

/* Review Screen */
.review-header {
    background: white;
    border-radius: var(--border-radius);
    padding: 20px;
    margin-bottom: 20px;
    box-shadow: var(--shadow);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.review-header h2 {
    color: var(--dark-color);
}

.review-content {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.review-item {
    background: white;
    border-radius: var(--border-radius);
    padding: 30px;
    box-shadow: var(--shadow);
}

.review-item-header {
    display: flex;
    align-items: center;
    gap: 15px;
    margin-bottom: 20px;
}

.review-number {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--accent-color);
    color: white;
    font-weight: bold;
    font-size: 1.2rem;
}

.review-status {
    padding: 5px 15px;
    border-radius: 20px;
    font-weight: 600;
    font-size: 0.9rem;
}

.review-status.correct {
    background: #d4edda;
    color: #155724;
}

.review-status.wrong {
    background: #f8d7da;
    color: #721c24;
}

.review-question {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--dark-color);
    margin-bottom: 20px;
    line-height: 1.6;
}

.review-options {
    display: flex;
    flex-direction: column;
    gap: 10px;
    margin-bottom: 20px;
}

.review-option {
    padding: 15px;
    border-radius: var(--border-radius);
    border: 2px solid transparent;
}

.review-option.user-answer {
    background: #fff3cd;
    border-color: var(--warning-color);
}

.review-option.correct-answer {
    background: #d4edda;
    border-color: var(--success-color);
    font-weight: 600;
}

.review-option.user-answer.correct-answer {
    background: #d4edda;
    border-color: var(--success-color);
}

.review-explanation {
    padding: 20px;
    background: #e7f3ff;
    border-left: 4px solid var(--accent-color);
    border-radius: var(--border-radius);
    line-height: 1.8;
}

.review-explanation strong {
    display: block;
    margin-bottom: 10px;
    color: var(--accent-color);
}

/* Ad Containers */
.ad-container {
    margin: 20px 0;
    text-align: center;
    overflow: hidden;
    border-radius: var(--border-radius);
    background: rgba(255, 255, 255, 0.1);
    min-height: 90px;
}

.ad-container ins {
    background: transparent;
}

.ad-result {
    margin: 25px 0;
    background: var(--light-color);
    border-radius: var(--border-radius);
    padding: 10px 0;
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Responsive Design */
@media (max-width: 768px) {
    header h1 {
        font-size: 1.8rem;
    }

    .welcome-card,
    .question-card,
    .result-card {
        padding: 25px;
    }

    .quiz-selector {
        padding: 20px;
    }

    .quiz-options {
        grid-template-columns: 1fr;
    }

    .option-content {
        min-height: 150px;
        padding: 20px;
    }

    .info-grid {
        grid-template-columns: 1fr;
    }

    .quiz-header {
        flex-direction: column;
    }

    .question-text {
        font-size: 1.2rem;
    }

    .option {
        padding: 15px;
        font-size: 1rem;
    }

    .navigation-buttons {
        flex-direction: column;
    }

    .btn {
        width: 100%;
    }

    .result-stats {
        flex-direction: column;
        gap: 20px;
    }

    .result-buttons {
        flex-direction: column;
    }

    .review-header {
        flex-direction: column;
        gap: 15px;
    }
}