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

:root {
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary: #64748b;
    --secondary-hover: #475569;
    --danger: #dc2626;
    --danger-hover: #b91c1c;
    --success: #16a34a;
    --warning: #d97706;
    --bg: #f8fafc;
    --bg-card: #ffffff;
    --text: #1e293b;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --shadow: 0 1px 3px rgba(0,0,0,0.1);
    --shadow-lg: 0 4px 6px rgba(0,0,0,0.1);
    --radius: 8px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

header {
    background: linear-gradient(135deg, var(--primary), var(--primary-hover));
    color: white;
    padding: 2rem;
    text-align: center;
    box-shadow: var(--shadow-lg);
}

header h1 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

.subtitle {
    opacity: 0.9;
    font-size: 1rem;
}

nav {
    background: var(--bg-card);
    border-bottom: 1px solid var(--border);
    padding: 0.5rem;
    display: flex;
    justify-content: center;
    gap: 0.5rem;
    flex-wrap: wrap;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow);
}

.nav-btn {
    padding: 0.75rem 1.5rem;
    border: none;
    background: transparent;
    color: var(--text-muted);
    font-size: 1rem;
    cursor: pointer;
    border-radius: var(--radius);
    transition: all 0.2s;
    font-weight: 500;
}

.nav-btn:hover {
    background: var(--bg);
    color: var(--text);
}

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

main {
    flex: 1;
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
    width: 100%;
}

.view {
    display: none;
}

.view.active {
    display: block;
}

h2 {
    margin-bottom: 1.5rem;
    color: var(--text);
    font-size: 1.5rem;
}

h3 {
    margin-bottom: 1rem;
    color: var(--text);
}

/* Buttons */
.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--radius);
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.2s;
    font-weight: 500;
}

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

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

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

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

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

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

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

/* Exams Grid */
.exams-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
}

.exam-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
    transition: transform 0.2s, box-shadow 0.2s;
}

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

.exam-card h3 {
    margin-bottom: 0.5rem;
    color: var(--primary);
}

.exam-card p {
    color: var(--text-muted);
    font-size: 0.9rem;
}

/* Topics Grid */
.topics-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
}

.topic-tag {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 2rem;
    padding: 0.5rem 1rem;
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.2s;
}

.topic-tag:hover {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

/* Practice Area */
.practice-header {
    margin-bottom: 2rem;
}

.practice-controls {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    align-items: center;
}

.practice-controls select {
    padding: 0.75rem 1rem;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    font-size: 1rem;
    background: var(--bg-card);
    min-width: 200px;
}

.practice-area {
    margin-top: 1.5rem;
}

.question-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    padding: 1rem;
    background: var(--bg-card);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

#question-counter {
    font-weight: 500;
    color: var(--text-muted);
}

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

.question-meta {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.badge {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.8rem;
    font-weight: 500;
    background: var(--bg);
    color: var(--text-muted);
}

.topic-badge {
    background: #dbeafe;
    color: #1e40af;
}

.type-badge {
    background: #fef3c7;
    color: #92400e;
}

.question-text {
    font-size: 1.1rem;
    line-height: 1.8;
    margin-bottom: 1.5rem;
    white-space: pre-wrap;
}

.question-options {
    margin-bottom: 1.5rem;
}

.option {
    padding: 1rem;
    margin-bottom: 0.5rem;
    border: 2px solid var(--border);
    border-radius: var(--radius);
    cursor: pointer;
    transition: all 0.2s;
}

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

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

.option.correct {
    border-color: var(--success);
    background: #dcfce7;
}

.option.incorrect {
    border-color: var(--danger);
    background: #fee2e2;
}

.answer-container {
    margin-top: 1.5rem;
    padding: 1.5rem;
    background: #f0fdf4;
    border: 1px solid #bbf7d0;
    border-radius: var(--radius);
}

.answer-container h3 {
    color: var(--success);
    margin-bottom: 0.5rem;
}

#answer-text {
    white-space: pre-wrap;
    line-height: 1.8;
}

/* Exam Area */
.exam-setup {
    text-align: center;
    max-width: 600px;
    margin: 0 auto;
}

.exam-info {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.5rem;
    margin: 1.5rem 0;
    text-align: left;
}

.exam-info ul {
    margin-top: 0.5rem;
    padding-left: 1.5rem;
}

.exam-info li {
    margin-bottom: 0.5rem;
}

.exam-controls {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

.exam-controls select {
    padding: 0.75rem 1rem;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    font-size: 1rem;
    background: var(--bg-card);
    min-width: 200px;
}

.exam-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 1.5rem;
    background: var(--bg-card);
    border-radius: var(--radius);
    margin-bottom: 1rem;
    box-shadow: var(--shadow);
}

.timer {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text);
}

.timer.warning {
    color: var(--warning);
}

.timer.danger {
    color: var(--danger);
    animation: pulse 1s infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

.exam-progress {
    font-weight: 500;
    color: var(--text-muted);
}

.exam-question-nav {
    margin-bottom: 1rem;
}

.questions-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(40px, 1fr));
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.question-btn {
    width: 40px;
    height: 40px;
    border: 2px solid var(--border);
    border-radius: var(--radius);
    background: var(--bg-card);
    cursor: pointer;
    font-weight: 500;
    transition: all 0.2s;
}

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

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

.question-btn.current {
    border-color: var(--primary);
    box-shadow: 0 0 0 2px var(--primary);
}

.exam-actions {
    text-align: center;
    margin-top: 1.5rem;
}

/* Exam Results */
.exam-results {
    text-align: center;
}

.results-summary {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1rem;
    margin: 2rem 0;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.result-item {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.5rem;
}

.result-label {
    display: block;
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

.result-value {
    display: block;
    font-size: 2rem;
    font-weight: 700;
    color: var(--text);
}

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

.result-value.incorrect {
    color: var(--danger);
}

.results-details {
    text-align: left;
    margin: 2rem 0;
}

.result-question {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1rem;
    margin-bottom: 1rem;
}

.result-question.correct {
    border-left: 4px solid var(--success);
}

.result-question.incorrect {
    border-left: 4px solid var(--danger);
}

.result-question.unanswered {
    border-left: 4px solid var(--secondary);
}

.result-question-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.5rem;
}

.result-question-status {
    font-weight: 600;
    font-size: 0.9rem;
}

.result-question-status.correct {
    color: var(--success);
}

.result-question-status.incorrect {
    color: var(--danger);
}

.result-question-status.unanswered {
    color: var(--secondary);
}

/* Stats */
.stats-info {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    text-align: center;
    color: var(--text-muted);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 1rem;
}

.stat-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
}

.stat-card h3 {
    margin-bottom: 1rem;
    color: var(--primary);
    font-size: 1rem;
}

.stat-bar {
    height: 8px;
    background: var(--bg);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 0.5rem;
}

.stat-bar-fill {
    height: 100%;
    background: var(--success);
    border-radius: 4px;
    transition: width 0.3s;
}

.stat-bar-fill.low {
    background: var(--danger);
}

.stat-bar-fill.medium {
    background: var(--warning);
}

.stat-info {
    display: flex;
    justify-content: space-between;
    font-size: 0.9rem;
    color: var(--text-muted);
}

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

footer {
    background: var(--bg-card);
    border-top: 1px solid var(--border);
    padding: 1.5rem;
    text-align: center;
    color: var(--text-muted);
    font-size: 0.9rem;
}

/* Responsive */
@media (max-width: 768px) {
    header h1 {
        font-size: 1.5rem;
    }
    
    main {
        padding: 1rem;
    }
    
    .practice-controls {
        flex-direction: column;
        align-items: stretch;
    }
    
    .practice-controls select {
        min-width: auto;
        width: 100%;
    }
    
    .question-nav {
        flex-direction: column;
        gap: 1rem;
    }
    
    .question-container {
        padding: 1rem;
    }
    
    .exam-header {
        flex-direction: column;
        gap: 1rem;
        text-align: center;
    }
    
    .results-summary {
        grid-template-columns: repeat(2, 1fr);
    }
}