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

:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --secondary-color: #8b5cf6;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --bg-color: #0f172a;
    --card-bg: #1e293b;
    --card-hover: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --border-color: #334155;
    --shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    padding: 20px;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    background: var(--card-bg);
    border-radius: 20px;
    padding: 40px;
    box-shadow: var(--shadow);
}

header {
    text-align: center;
    margin-bottom: 40px;
    padding-bottom: 30px;
    border-bottom: 2px solid var(--border-color);
}

header h1 {
    font-size: 2.5rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 10px;
}

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

/* Tabs */
.tabs {
    display: flex;
    gap: 10px;
    margin-bottom: 30px;
    border-bottom: 2px solid var(--border-color);
}

.tab-btn {
    background: transparent;
    border: none;
    color: var(--text-secondary);
    padding: 15px 30px;
    font-size: 1rem;
    cursor: pointer;
    border-radius: 10px 10px 0 0;
    transition: all 0.3s ease;
    font-weight: 600;
}

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

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

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn 0.3s ease;
}

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

/* Progress Bar */
.progress-bar {
    width: 100%;
    height: 30px;
    background: var(--bg-color);
    border-radius: 15px;
    overflow: hidden;
    margin-bottom: 10px;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    width: 0%;
    transition: width 0.5s ease;
    display: flex;
    align-items: center;
    justify-content: flex-end;
    padding-right: 10px;
    color: white;
    font-weight: bold;
}

.progress-text {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 30px;
    font-size: 0.95rem;
}

/* Layer Cards */
.layer-card {
    background: var(--bg-color);
    border-radius: 15px;
    margin-bottom: 25px;
    overflow: hidden;
    border: 2px solid var(--border-color);
    transition: all 0.3s ease;
}

.layer-card:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
}

.layer-card.completed {
    border-color: var(--success-color);
}

.layer-header {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary-color));
    padding: 25px;
    cursor: pointer;
}

.layer-card.completed .layer-header {
    background: linear-gradient(135deg, var(--success-color), #059669);
}

.layer-header h2 {
    font-size: 1.8rem;
    margin-bottom: 5px;
}

.layer-tagline {
    color: rgba(255, 255, 255, 0.9);
    font-size: 1rem;
    font-style: italic;
}

.layer-content {
    padding: 30px;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
}

.concept {
    background: var(--card-bg);
    padding: 20px;
    border-radius: 10px;
    border-left: 4px solid var(--primary-color);
    transition: all 0.3s ease;
}

.concept:hover {
    transform: translateX(5px);
    border-left-color: var(--secondary-color);
    background: var(--card-hover);
}

.concept h3 {
    color: var(--primary-color);
    font-size: 1.1rem;
    margin-bottom: 10px;
}

.concept p {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.complete-btn {
    grid-column: 1 / -1;
    background: var(--success-color);
    color: white;
    border: none;
    padding: 15px 30px;
    border-radius: 10px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    margin-top: 10px;
}

.complete-btn:hover {
    background: #059669;
    transform: scale(1.02);
}

.complete-btn.completed {
    background: var(--border-color);
    cursor: not-allowed;
}

.complete-btn.completed::before {
    content: "✓ ";
}

/* Quiz Styles */
.quiz-container {
    max-width: 800px;
    margin: 0 auto;
}

.quiz-start {
    text-align: center;
    padding: 60px 40px;
    background: var(--bg-color);
    border-radius: 15px;
}

.quiz-start h2 {
    font-size: 2rem;
    margin-bottom: 20px;
    color: var(--primary-color);
}

.quiz-start p {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 30px;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    border: none;
    padding: 15px 40px;
    border-radius: 10px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 20px rgba(99, 102, 241, 0.3);
}

.btn-secondary {
    background: var(--card-hover);
    color: white;
    border: 2px solid var(--border-color);
    padding: 15px 40px;
    border-radius: 10px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    margin-left: 10px;
}

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

.quiz-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px;
    background: var(--bg-color);
    border-radius: 10px;
    margin-bottom: 30px;
}

.quiz-progress, .quiz-score {
    font-size: 1.1rem;
    font-weight: 600;
}

.quiz-score span {
    color: var(--success-color);
    font-size: 1.3rem;
}

.question-container {
    background: var(--bg-color);
    padding: 40px;
    border-radius: 15px;
    margin-bottom: 30px;
}

.question {
    font-size: 1.3rem;
    margin-bottom: 30px;
    color: var(--text-primary);
    font-weight: 600;
}

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

.option {
    background: var(--card-bg);
    border: 2px solid var(--border-color);
    padding: 20px;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 1rem;
}

.option:hover {
    border-color: var(--primary-color);
    background: var(--card-hover);
    transform: translateX(5px);
}

.option.selected {
    border-color: var(--primary-color);
    background: var(--primary-dark);
}

.option.correct {
    border-color: var(--success-color);
    background: rgba(16, 185, 129, 0.2);
}

.option.incorrect {
    border-color: var(--danger-color);
    background: rgba(239, 68, 68, 0.2);
}

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

.quiz-navigation {
    text-align: center;
}

/* Quiz Results */
.quiz-results {
    text-align: center;
    padding: 40px;
}

.quiz-results h2 {
    font-size: 2.5rem;
    margin-bottom: 30px;
    color: var(--primary-color);
}

.results-score {
    margin: 40px 0;
}

.score-circle {
    width: 200px;
    height: 200px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto;
    font-size: 3rem;
    font-weight: bold;
    box-shadow: 0 10px 40px rgba(99, 102, 241, 0.4);
}

#resultsMessage {
    font-size: 1.3rem;
    color: var(--text-secondary);
    margin-bottom: 40px;
}

.results-breakdown {
    background: var(--bg-color);
    padding: 30px;
    border-radius: 15px;
    margin: 30px 0;
    text-align: left;
}

.results-breakdown h3 {
    color: var(--primary-color);
    margin-bottom: 20px;
    text-align: center;
}

.layer-result {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px;
    background: var(--card-bg);
    border-radius: 8px;
    margin-bottom: 10px;
}

.layer-result-name {
    font-weight: 600;
}

.layer-result-score {
    font-weight: bold;
    font-size: 1.1rem;
}

.layer-result-score.good {
    color: var(--success-color);
}

.layer-result-score.medium {
    color: var(--warning-color);
}

.layer-result-score.poor {
    color: var(--danger-color);
}

/* Feedback Message */
.feedback {
    margin-top: 15px;
    padding: 15px;
    border-radius: 8px;
    font-weight: 600;
    animation: slideIn 0.3s ease;
}

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

.feedback.correct {
    background: rgba(16, 185, 129, 0.2);
    color: var(--success-color);
    border: 1px solid var(--success-color);
}

.feedback.incorrect {
    background: rgba(239, 68, 68, 0.2);
    color: var(--danger-color);
    border: 1px solid var(--danger-color);
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 20px;
    }

    header h1 {
        font-size: 2rem;
    }

    .layer-content {
        grid-template-columns: 1fr;
    }

    .tabs {
        flex-direction: column;
    }

    .tab-btn {
        border-radius: 10px;
    }

    .quiz-header {
        flex-direction: column;
        gap: 10px;
    }

    .btn-secondary {
        margin-left: 0;
        margin-top: 10px;
    }

    .score-circle {
        width: 150px;
        height: 150px;
        font-size: 2.5rem;
    }
}