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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: #333;
}

.container {
    max-width: 1800px; /* Further increased to utilize much more screen space */
    margin: 0 auto;
    padding: 20px;
    width: 95%; /* Use 95% of available screen width */
}

header {
    background: rgba(255, 255, 255, 0.95);
    padding: 30px;
    border-radius: 15px;
    margin-bottom: 30px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
}

.header-top {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.header-top h1 {
    text-align: left;
    margin: 0;
}


.course-info {
    text-align: center;
}

header h1 {
    color: #2c3e50;
    font-size: 2.5rem;
    margin-bottom: 15px;
    font-weight: 700;
}

.course-info {
    display: flex;
    justify-content: center;
    gap: 40px;
    font-size: 1.1rem;
}

.course-info p {
    color: #555;
}

.page {
    display: none;
    background: rgba(255, 255, 255, 0.95);
    border-radius: 15px;
    padding: 30px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
    min-height: 600px;
}

.page.active {
    display: block;
}

#home-page h2 {
    text-align: center;
    color: #2c3e50;
    font-size: 2rem;
    margin-bottom: 20px;
}

#home-page p {
    text-align: center;
    font-size: 1.2rem;
    color: #666;
    margin-bottom: 40px;
}

.module-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 25px;
    margin-top: 30px;
}

.welcome-section {
    text-align: center;
    margin-bottom: 40px;
}

.progress-overview {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 10px;
    margin-top: 20px;
    border-left: 4px solid #667eea;
}

.progress-overview h3 {
    color: #2c3e50;
    margin-bottom: 15px;
}

#progress-bars {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 15px;
}

.progress-bar {
    background: #e9ecef;
    border-radius: 10px;
    padding: 10px;
    text-align: center;
}

.progress-fill {
    background: linear-gradient(135deg, #28a745, #20c997);
    height: 8px;
    border-radius: 4px;
    transition: width 0.3s ease;
}

.module-card {
    background: linear-gradient(145deg, #ffffff, #f0f0f0);
    border-radius: 15px;
    padding: 30px;
    text-align: center;
    transition: all 0.3s ease;
    cursor: pointer;
    border: 2px solid transparent;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
    position: relative;
}

.module-status {
    position: absolute;
    top: 15px;
    right: 15px;
    padding: 5px 12px;
    border-radius: 15px;
    font-size: 0.8rem;
    font-weight: 600;
}

.status-completed {
    background: #28a745;
    color: white;
}

.status-partial {
    background: #ffc107;
    color: #212529;
}

.status-in-progress {
    background: #17a2b8;
    color: white;
}

.module-status:not([class*="status-"]) {
    background: #6c757d;
    color: white;
}

.module-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.2);
    border-color: #667eea;
}

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

.module-card h3 {
    color: #2c3e50;
    font-size: 1.4rem;
    margin-bottom: 10px;
}

.module-card p {
    color: #666;
    margin-bottom: 20px;
    line-height: 1.5;
}

.start-btn {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    border: none;
    padding: 12px 25px;
    border-radius: 25px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.start-btn:hover {
    transform: scale(1.05);
    box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.lab-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 2px solid #e0e0e0;
}

.lab-header-left {
    display: flex;
    align-items: center;
    gap: 20px;
}

.lab-header-left h2 {
    margin: 0;
}

.kepler-law-selector {
    text-align: center;
    margin-bottom: 40px;
    background: rgba(255, 255, 255, 0.9);
    padding: 25px;
    border-radius: 15px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}

.kepler-law-selector h3 {
    color: #2c3e50;
    margin-bottom: 25px;
    font-size: 1.4rem;
    font-weight: 600;
}

.law-buttons {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
    max-width: 900px;
    margin: 0 auto;
}

.law-btn {
    background: linear-gradient(145deg, #ffffff, #f8f9fa);
    border: 3px solid #e9ecef;
    border-radius: 15px;
    padding: 20px;
    cursor: pointer;
    transition: all 0.3s ease;
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    position: relative;
    overflow: hidden;
}

.law-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(111, 66, 193, 0.2);
    border-color: #6f42c1;
}

.law-btn.active {
    background: linear-gradient(145deg, #6f42c1, #8a2be2);
    border-color: #6f42c1;
    color: white;
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(111, 66, 193, 0.3);
}

.law-number {
    background: rgba(111, 66, 193, 0.1);
    color: #6f42c1;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    font-weight: bold;
    margin-bottom: 5px;
}

.law-btn.active .law-number {
    background: rgba(255, 255, 255, 0.2);
    color: white;
}

.law-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: #2c3e50;
}

.law-btn.active .law-title {
    color: white;
}

.law-description {
    font-size: 0.9rem;
    color: #666;
    line-height: 1.4;
    text-align: center;
}

.law-btn.active .law-description {
    color: rgba(255, 255, 255, 0.9);
}

.lab-progress {
    background: #e8f4fd;
    padding: 10px 20px;
    border-radius: 20px;
    border-left: 4px solid #007bff;
    font-weight: 600;
    color: #007bff;
}

.back-btn {
    background: #6c757d;
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 20px;
    cursor: pointer;
    font-size: 1rem;
    margin-right: 20px;
    transition: background 0.3s ease;
}

.back-btn:hover {
    background: #5a6268;
}

.lab-header h2 {
    color: #2c3e50;
    font-size: 1.8rem;
}

.experiment-tabs {
    display: flex;
    gap: 10px;
    margin-bottom: 25px;
    border-bottom: 2px solid #e0e0e0;
}

.tab-btn {
    background: transparent;
    border: none;
    padding: 12px 24px;
    cursor: pointer;
    font-weight: 600;
    color: #666;
    border-bottom: 3px solid transparent;
    transition: all 0.3s ease;
}

.tab-btn.active {
    color: #667eea;
    border-bottom-color: #667eea;
}

.tab-btn:hover {
    color: #667eea;
    background: rgba(102, 126, 234, 0.1);
}

.experiment {
    display: none;
}

.experiment.active {
    display: block;
}

.lab-content {
    /* Updated for Kepler layout - using flexbox in simulation-container instead */
    min-height: 80vh;
    width: 100%;
}

.experiment-panel {
    /* Updated for Kepler layout - no background/padding since simulation-container handles it */
    height: 100%;
    width: 100%;
}

.experiment-panel h3 {
    color: #2c3e50;
    margin-bottom: 20px;
    font-size: 1.3rem;
}

.animation-controls-container {
    display: flex;
    gap: 20px;
    margin-bottom: 20px;
    align-items: flex-start;
    width: 100%;
    max-height: 600px;
}

canvas {
    border: 2px solid #ddd;
    border-radius: 8px;
    background: white;
    display: block;
    flex: 2;
    max-width: calc(100% - 400px);
    min-width: 450px;
    height: auto;
}

.animation-controls-container .controls {
    flex: 1;
    background: #f8f9fa;
    padding: 20px;
    border-radius: 10px;
    border: 1px solid #e0e0e0;
    max-height: 600px;
    height: fit-content;
    overflow-y: auto;
    overflow-x: visible;
    width: 100%;
    max-width: 380px;
    min-width: 320px;
}

.controls {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.animation-controls-container .controls {
    gap: 20px;
}

.control-group, .charge-controls, .object-controls, .wave-source-controls {
    background: #f8f9fa;
    padding: 15px;
    border-radius: 10px;
    border-left: 4px solid #667eea;
}

.control-group h4, .charge-controls h4, .object-controls h4 {
    color: #2c3e50;
    margin-bottom: 15px;
    font-size: 1.1rem;
}

.charge-set, .object-set {
    background: white;
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 15px;
    border: 1px solid #dee2e6;
}

.charge-set h5, .object-set h5 {
    color: #495057;
    margin-bottom: 10px;
    font-size: 1rem;
}

.answer-inputs {
    display: flex;
    flex-direction: column;
    gap: 10px;
    margin-top: 10px;
}

.answer-inputs label {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.answer-inputs input {
    width: 120px;
    padding: 5px 10px;
    border: 1px solid #ccc;
    border-radius: 5px;
}

.controls label {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-weight: 500;
    color: #555;
}

.controls input[type="range"] {
    width: 150px;
    margin-left: 10px;
}

.controls button {
    background: linear-gradient(135deg, #28a745, #20c997);
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 20px;
    cursor: pointer;
    font-weight: 600;
    transition: all 0.3s ease;
    margin: 5px;
}

.controls button:hover {
    transform: scale(1.05);
    box-shadow: 0 4px 15px rgba(40, 167, 69, 0.3);
}

.results-panel {
    background: #e8f4fd;
    padding: 30px; /* Increased padding for better breathing room */
    border-radius: 12px;
    border-left: 4px solid #007bff;
    max-height: 85vh; /* Slightly taller */
    overflow-y: auto;
    box-shadow: 0 4px 15px rgba(0, 123, 255, 0.1); /* Added subtle shadow */
}

.question-section {
    margin-bottom: 30px;
}

.question {
    background: white;
    padding: 25px; /* Increased padding */
    border-radius: 12px;
    margin-bottom: 25px; /* Increased margin between questions */
    border-left: 4px solid #17a2b8;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05); /* Added subtle shadow */
}

.question h5 {
    color: #2c3e50;
    margin-bottom: 10px;
    font-size: 1.1rem;
}

.question p {
    color: #495057;
    margin-bottom: 15px;
    line-height: 1.5;
}

.question textarea {
    width: 100%;
    min-height: 80px;
    padding: 10px;
    border: 2px solid #dee2e6;
    border-radius: 8px;
    font-family: inherit;
    font-size: 0.95rem;
    resize: vertical;
}

.question input[type="number"], .question input[type="text"] {
    width: 200px;
    padding: 8px 12px;
    border: 2px solid #dee2e6;
    border-radius: 8px;
    font-size: 0.95rem;
}

.question select {
    width: 250px;
    padding: 8px 12px;
    border: 2px solid #dee2e6;
    border-radius: 8px;
    font-size: 0.95rem;
    background: white;
}

.question-feedback {
    margin-top: 10px;
    padding: 10px;
    border-radius: 6px;
    font-weight: 600;
    display: none;
}

.question-feedback.correct {
    background: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
    display: block;
}

.question-feedback.partial {
    background: #fff3cd;
    color: #856404;
    border: 1px solid #ffeaa7;
    display: block;
}

.question-feedback.incorrect {
    background: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
    display: block;
}

.submission-section {
    text-align: center;
    padding: 20px;
    background: white;
    border-radius: 10px;
    border-left: 4px solid #28a745;
}

.submit-btn {
    background: linear-gradient(135deg, #28a745, #20c997);
    color: white;
    border: none;
    padding: 15px 30px;
    border-radius: 25px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.submit-btn:hover {
    transform: scale(1.05);
    box-shadow: 0 6px 20px rgba(40, 167, 69, 0.3);
}

.lab-score {
    margin-top: 20px;
    padding: 20px;
    border-radius: 10px;
    display: none;
}

.lab-score h4 {
    margin-bottom: 15px;
    font-size: 1.3rem;
}

.score-details p {
    margin-bottom: 8px;
    font-size: 1rem;
}

.grade-a {
    background: #d4edda;
    color: #155724;
    border: 2px solid #28a745;
    display: block;
}

.grade-b {
    background: #cce7ff;
    color: #004085;
    border: 2px solid #007bff;
    display: block;
}

.grade-c {
    background: #fff3cd;
    color: #856404;
    border: 2px solid #ffc107;
    display: block;
}

.grade-d {
    background: #ffe6cc;
    color: #8b4513;
    border: 2px solid #ff8c00;
    display: block;
}

.grade-f {
    background: #f8d7da;
    color: #721c24;
    border: 2px solid #dc3545;
    display: block;
}

.live-calculations, .live-measurements, .live-data {
    background: #f1f3f4;
    padding: 15px;
    border-radius: 8px;
    margin-top: 20px;
    border-left: 4px solid #6c757d;
}

.live-calculations h4, .live-measurements h4, .live-data h4 {
    color: #495057;
    margin-bottom: 10px;
    font-size: 1rem;
}

.live-calculations p, .live-measurements p, .live-data p {
    margin-bottom: 5px;
    font-size: 0.9rem;
    color: #6c757d;
}

.live-calculations span, .live-measurements span, .live-data span {
    font-weight: bold;
    color: #495057;
}

.orbital-data, .area-measurements {
    background: #f8f9fa;
    padding: 15px;
    border-radius: 8px;
    margin-top: 15px;
    border-left: 4px solid #6f42c1;
}

.harmonic-data {
    background: #f8f9fa;
    padding: 15px;
    border-radius: 8px;
    margin-top: 15px;
    border-left: 4px solid #6f42c1;
    height: auto;
    min-height: fit-content;
}

.orbital-data h4, .area-measurements h4, .harmonic-data h4 {
    color: #6f42c1;
    margin-bottom: 10px;
    font-size: 1rem;
}

.orbital-data p, .area-measurements p, .harmonic-data p {
    margin-bottom: 5px;
    font-size: 0.9rem;
    color: #495057;
}

.orbital-data span, .area-measurements span, .harmonic-data span {
    font-weight: bold;
    color: #6f42c1;
}

.planet-controls {
    display: flex;
    flex-direction: column;
    gap: 15px;
    margin-bottom: 20px;
}

.animation-controls-container .planet-controls {
    gap: 12px;
}

.planet-set {
    background: white;
    padding: 15px;
    border-radius: 8px;
    border: 1px solid #dee2e6;
    border-left: 3px solid #6f42c1;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.05);
}

.animation-controls-container .planet-set {
    padding: 10px;
    margin-bottom: 6px;
}

.animation-controls-container .planet-set h5 {
    font-size: 0.95rem;
    margin-bottom: 8px;
}

.animation-controls-container .planet-set label {
    font-size: 0.85rem;
    margin-bottom: 6px;
}

.planet-set h5 {
    color: #6f42c1;
    margin-bottom: 15px; /* Increased margin */
    font-size: 1.1rem; /* Slightly larger font */
    font-weight: 600;
}

.planet-set label {
    display: block;
    margin-bottom: 12px; /* Added spacing between controls */
    font-weight: 500;
    color: #555;
}

.orbit-controls, .area-controls, .system-controls {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    align-items: center;
    margin-top: 15px;
    padding-top: 15px;
    border-top: 1px solid #dee2e6;
}

.orbit-controls button, .area-controls button, .system-controls button {
    background: linear-gradient(135deg, #6f42c1, #8a2be2);
    color: white;
    border: none;
    padding: 8px 16px;
    border-radius: 20px;
    cursor: pointer;
    font-weight: 600;
    transition: all 0.3s ease;
    font-size: 0.9rem;
}

.orbit-controls button:hover, .area-controls button:hover, .system-controls button:hover {
    transform: scale(1.05);
    box-shadow: 0 4px 15px rgba(111, 66, 193, 0.3);
}

.period-data, .ratio-verification {
    background: white;
    padding: 10px;
    border-radius: 6px;
    margin-bottom: 10px;
    border-left: 3px solid #28a745;
}

.period-data p, .ratio-verification p {
    margin-bottom: 5px;
    font-size: 0.9rem;
}

.kepler-summary {
    background: #f1f3f4;
    padding: 20px;
    border-radius: 10px;
    margin-top: 20px;
    border-left: 4px solid #6f42c1;
}

.kepler-summary h4 {
    color: #2c3e50;
    margin-bottom: 15px;
    font-size: 1.2rem;
}

.laws-summary {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 15px;
}

.law-summary {
    background: white;
    padding: 15px;
    border-radius: 8px;
    border-left: 4px solid #6f42c1;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

.law-summary h5 {
    color: #6f42c1;
    margin-bottom: 10px;
    font-size: 1rem;
}

.law-summary p {
    color: #495057;
    margin-bottom: 5px;
    font-size: 0.9rem;
    line-height: 1.4;
}

.results-panel h4 {
    color: #2c3e50;
    margin-bottom: 15px;
    font-size: 1.2rem;
}

.results-panel p {
    margin-bottom: 10px;
    line-height: 1.5;
    color: #555;
}

.results-panel span {
    font-weight: bold;
    color: #007bff;
}

@media (max-width: 768px) {
    .container {
        padding: 10px;
    }
    
    .header-top {
        flex-direction: column;
        gap: 15px;
        text-align: center;
    }
    
    .header-top h1 {
        text-align: center;
        font-size: 2rem;
    }
    
    .course-info {
        flex-direction: column;
        gap: 10px;
    }
    
    .module-grid {
        grid-template-columns: 1fr;
    }
    
    .lab-content {
        grid-template-columns: 1fr;
    }
    
    .experiment-tabs {
        flex-wrap: wrap;
    }
    
    .tab-btn {
        flex: 1;
        min-width: 120px;
    }
    
    canvas {
        width: 100%;
        height: auto;
    }
    
    .charge-controls, .object-controls {
        padding: 10px;
    }
    
    .question input[type="number"], .question input[type="text"], .question select {
        width: 100%;
    }
    
    .answer-inputs {
        gap: 15px;
    }
    
    .answer-inputs label {
        flex-direction: column;
        align-items: flex-start;
        gap: 5px;
    }
    
    .answer-inputs input {
        width: 100%;
    }
    
    .planet-controls {
        grid-template-columns: 1fr;
        gap: 20px; /* Maintain good spacing on mobile */
    }
    
    .lab-content {
        grid-template-columns: 1fr; /* Stack vertically on mobile */
        gap: 25px;
    }
    
    .laws-summary {
        grid-template-columns: 1fr;
    }
    
    .orbit-controls, .area-controls, .system-controls {
        flex-direction: column;
        align-items: stretch;
    }
    
    .orbit-controls button, .area-controls button, .system-controls button {
        width: 100%;
        margin-bottom: 5px;
    }
    
    .lab-header {
        flex-direction: column;
        align-items: stretch;
        text-align: center;
    }
    
    .lab-header-left {
        flex-direction: column;
        gap: 10px;
    }
    
    .law-buttons {
        grid-template-columns: 1fr;
    }
    
    .kepler-law-selector {
        padding: 15px;
    }
}

.animation-running {
    animation: pulse 2s infinite;
}

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

/* Kepler-specific styles */
.kepler-tabs-container {
    background: white;
    border-radius: 15px;
    margin-bottom: 30px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
    overflow: hidden;
}

.kepler-tabs {
    display: flex;
    gap: 0;
    margin: 0;
    border-bottom: none;
}

.kepler-tab-btn {
    flex: 1;
    background: #f8f9fa;
    border: none;
    padding: 20px 15px;
    cursor: pointer;
    font-weight: 600;
    color: #666;
    font-size: 1.1rem;
    transition: all 0.3s ease;
    border-right: 1px solid #dee2e6;
    text-align: center;
    position: relative;
}

.kepler-tab-btn:last-child {
    border-right: none;
}

.kepler-tab-btn:hover {
    background: rgba(102, 126, 234, 0.1);
    color: #667eea;
    transform: translateY(-2px);
}

.kepler-tab-btn.active {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    box-shadow: inset 0 3px 10px rgba(0, 0, 0, 0.1);
}

.kepler-tab-btn.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, #f39c12, #e74c3c);
}

.simulation-container {
    display: flex;
    gap: 40px;
    min-height: 80vh;
    height: auto;
    width: 100%;
}

.simulation-area {
    flex: 3;
    background: #f8f9fa;
    padding: 30px;
    border-radius: 15px;
    border: 1px solid #e0e0e0;
    min-width: 0; /* Prevent flex item from shrinking below content size */
    overflow-y: auto;
    height: 100%;
}

.questions-area {
    flex: 1;
    background: linear-gradient(135deg, #e8f4fd, #f0f8ff);
    padding: 25px;
    border-radius: 15px;
    border: 1px solid #007bff;
    box-shadow: 0 4px 15px rgba(0, 123, 255, 0.1);
    height: 100%;
    overflow-y: auto;
    min-width: 280px;
    max-width: 350px;
    display: flex;
    flex-direction: column;
}

.questions-area h4 {
    color: #007bff;
    margin-bottom: 20px;
    font-size: 1.3rem;
    text-align: center;
    border-bottom: 2px solid #007bff;
    padding-bottom: 10px;
}

.question-box {
    background: white;
    padding: 20px;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    border-left: 4px solid #007bff;
    margin-bottom: 20px;
    flex-grow: 1;
}

.question-box p {
    color: #2c3e50;
    margin-bottom: 15px;
    line-height: 1.6;
    font-size: 1rem;
}

.question-box input[type="number"] {
    width: 150px;
    padding: 8px 12px;
    border: 2px solid #ddd;
    border-radius: 6px;
    font-size: 1rem;
    margin-right: 8px;
    transition: border-color 0.3s ease;
}

.question-box input[type="number"]:focus {
    outline: none;
    border-color: #007bff;
    box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.1);
}

.unit-label {
    font-weight: bold;
    color: #666;
    margin-left: 5px;
}

.answer-options {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.answer-options label {
    display: flex;
    align-items: center;
    gap: 10px;
    background: #f8f9fa;
    padding: 12px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
    border: 2px solid transparent;
}

.answer-options label:hover {
    background: #e3f2fd;
    border-color: #2196f3;
    transform: translateX(5px);
}

.answer-options input[type="radio"] {
    margin: 0;
    transform: scale(1.2);
    accent-color: #007bff;
}

.answer-options label:has(input:checked) {
    background: #cce7ff;
    border-color: #007bff;
    font-weight: 600;
    color: #004085;
}

.submit-area {
    margin-top: auto;
    padding-top: 20px;
    border-top: 2px solid #007bff;
    text-align: center;
}

.submit-area .submit-btn {
    background: linear-gradient(135deg, #28a745, #20c997);
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: 25px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    width: 100%;
    max-width: 200px;
}

.submit-area .submit-btn:hover {
    transform: scale(1.05);
    box-shadow: 0 4px 15px rgba(40, 167, 69, 0.3);
}

/* Old submit-section styles removed - now using submit-area within questions */

.submit-area .quiz-results {
    margin-top: 15px;
    padding: 15px;
    border-radius: 8px;
    display: none;
}

.submit-area .quiz-results.show {
    display: block;
}

.submit-area .quiz-results.excellent {
    background: #d4edda;
    color: #155724;
    border: 2px solid #28a745;
}

.submit-area .quiz-results.good {
    background: #cce7ff;
    color: #004085;
    border: 2px solid #007bff;
}

.submit-area .quiz-results.needs-improvement {
    background: #fff3cd;
    color: #856404;
    border: 2px solid #ffc107;
}

.submit-area .quiz-results h4 {
    margin-bottom: 10px;
    font-size: 1.1rem;
}

.submit-area .quiz-results p {
    margin-bottom: 5px;
    font-size: 0.9rem;
}

@media (max-width: 768px) {
    .kepler-tabs {
        flex-direction: column;
    }
    
    .kepler-tab-btn {
        border-right: none;
        border-bottom: 1px solid #dee2e6;
    }
    
    .kepler-tab-btn:last-child {
        border-bottom: none;
    }
    
    .simulation-container {
        flex-direction: column;
        gap: 20px;
    }
    
    .simulation-area, .questions-area {
        flex: none;
        max-height: none;
    }
}