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

:root {
    --primary-color: #FF9900;
    --primary-dark: #EC7211;
    --secondary-color: #232F3E;
    --accent-color: #146EB4;
    --success-color: #1D8102;
    --danger-color: #D13212;
    --warning-color: #FF9900;
    --text-primary: #232F3E;
    --text-secondary: #687078;
    --bg-primary: #FFFFFF;
    --bg-secondary: #F5F5F5;
    --border-color: #D5DBDB;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 4px 16px rgba(0, 0, 0, 0.15);
}

/* Dark mode color scheme */
body.dark-mode {
    --primary-color: #FFB84D;
    --primary-dark: #FF9900;
    --secondary-color: #E8EAF6;
    --accent-color: #64B5F6;
    --success-color: #4CAF50;
    --danger-color: #EF5350;
    --warning-color: #FFB84D;
    --text-primary: #E8EAF6;
    --text-secondary: #B0BEC5;
    --bg-primary: #1A1A2E;
    --bg-secondary: #16213E;
    --border-color: #2D3748;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 4px 16px rgba(0, 0, 0, 0.4);
}

body.dark-mode {
    background: linear-gradient(135deg, #1a1a2e 0%, #16213e 100%);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
    color: var(--text-primary);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
}

.screen {
    display: none;
    animation: fadeIn 0.3s ease-in;
}

.screen.active {
    display: block;
}

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

/* Welcome Screen */
.welcome-content {
    background: var(--bg-primary);
    border-radius: 20px;
    padding: 60px 40px;
    text-align: center;
    box-shadow: var(--shadow-lg);
    max-width: 800px;
    margin: 40px auto;
}

.welcome-content h1 {
    color: var(--secondary-color);
    font-size: 2.5rem;
    margin-bottom: 10px;
    font-weight: 700;
}

.welcome-content h2 {
    color: var(--primary-color);
    font-size: 2rem;
    margin-bottom: 10px;
    font-weight: 600;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
    margin-bottom: 40px;
}

.exam-info {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 40px;
}

.info-card {
    background: var(--bg-secondary);
    padding: 25px;
    border-radius: 12px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 10px;
    transition: transform 0.2s;
}

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

.info-icon {
    font-size: 2.5rem;
}

.info-text {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 5px;
}

.info-text strong {
    color: var(--text-primary);
    font-size: 0.9rem;
    font-weight: 600;
}

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

/* Buttons */
.btn {
    padding: 14px 32px;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    outline: none;
    font-family: inherit;
}

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

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

.btn-primary:hover:not(:disabled) {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(255, 153, 0, 0.3);
}

.btn-secondary {
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
}

.btn-secondary:hover:not(:disabled) {
    background: var(--bg-primary);
    border-color: var(--primary-color);
    transform: translateY(-2px);
}

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

.btn-success:hover:not(:disabled) {
    background: #156d01;
    transform: translateY(-2px);
}

.btn-flag {
    background: var(--bg-primary);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
}

.btn-flag:hover:not(:disabled) {
    border-color: var(--warning-color);
    color: var(--warning-color);
}

.btn-flag.flagged {
    background: var(--warning-color);
    color: white;
    border-color: var(--warning-color);
}

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

.btn-check:hover:not(:disabled) {
    background: #0d5a94;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(20, 110, 180, 0.3);
}

/* Exam Screen */
#examScreen {
    background: var(--bg-primary);
    border-radius: 20px;
    padding: 30px;
    box-shadow: var(--shadow-lg);
}

.exam-header {
    margin-bottom: 30px;
}

.progress-bar {
    height: 8px;
    background: var(--bg-secondary);
    border-radius: 10px;
    overflow: hidden;
    margin-bottom: 15px;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--primary-dark));
    border-radius: 10px;
    transition: width 0.3s ease;
    width: 0%;
}

.exam-stats {
    display: flex;
    justify-content: space-between;
    align-items: center;
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.timer {
    font-weight: 600;
    color: var(--accent-color);
}

.question-container {
    background: var(--bg-primary);
    padding: 30px;
    border-radius: 12px;
    margin-bottom: 25px;
    border: 1px solid var(--border-color);
}

.question-header {
    margin-bottom: 20px;
}

.question-label {
    background: var(--primary-color);
    color: white;
    padding: 6px 16px;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 600;
}

.question-text {
    font-size: 1.2rem;
    line-height: 1.6;
    color: var(--text-primary);
    margin-bottom: 25px;
    font-weight: 500;
}

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

.option {
    display: flex;
    align-items: center;
    padding: 18px 20px;
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.2s;
    position: relative;
}

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

.option.selected {
    background: var(--bg-primary);
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(255, 153, 0, 0.1);
}

.option.correct {
    background: #e8f5e9;
    border-color: var(--success-color);
}

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

.option input[type="radio"],
.option input[type="checkbox"] {
    margin-right: 12px;
    width: 20px;
    height: 20px;
    cursor: pointer;
}

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

/* Study Mode Feedback Styles */
.option.study-correct-answer {
    border-color: var(--success-color);
    border-width: 2px;
}

.option.study-correct {
    background: #e8f5e9;
    border-color: var(--success-color);
    box-shadow: 0 0 0 3px rgba(29, 129, 2, 0.1);
}

body.dark-mode .option.study-correct {
    background: rgba(76, 175, 80, 0.2);
}

.option.study-incorrect {
    background: #ffebee;
    border-color: var(--danger-color);
    box-shadow: 0 0 0 3px rgba(209, 50, 18, 0.1);
}

body.dark-mode .option.study-incorrect {
    background: rgba(239, 83, 80, 0.2);
}

/* Study Mode Explanation */
.study-mode-explanation {
    margin-top: 25px;
    padding: 20px 24px;
    background: var(--bg-secondary);
    border-left: 4px solid var(--accent-color);
    border-radius: 8px;
    animation: slideDown 0.3s ease-out;
}

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

.explanation-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 12px;
    color: var(--accent-color);
    font-size: 1rem;
}

.explanation-icon {
    font-size: 1.3rem;
}

.explanation-content {
    color: var(--text-primary);
    line-height: 1.6;
    font-size: 0.95rem;
}

/* Study Mode Toggle */
.study-mode-toggle-container {
    margin: 20px 0 30px;
    display: flex;
    justify-content: center;
}

.study-mode-toggle {
    display: flex;
    align-items: center;
    gap: 15px;
    padding: 20px 30px;
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
}

.study-mode-toggle:hover {
    border-color: var(--accent-color);
    box-shadow: var(--shadow);
}

.study-mode-toggle input[type="checkbox"] {
    position: absolute;
    opacity: 0;
    width: 0;
    height: 0;
}

.toggle-slider {
    position: relative;
    width: 56px;
    height: 30px;
    background: var(--border-color);
    border-radius: 30px;
    transition: all 0.3s ease;
    flex-shrink: 0;
}

.toggle-slider::before {
    content: '';
    position: absolute;
    width: 24px;
    height: 24px;
    left: 3px;
    top: 3px;
    background: white;
    border-radius: 50%;
    transition: all 0.3s ease;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.study-mode-toggle input[type="checkbox"]:checked ~ .toggle-slider {
    background: var(--accent-color);
}

.study-mode-toggle input[type="checkbox"]:checked ~ .toggle-slider::before {
    transform: translateX(26px);
}

.toggle-label {
    display: flex;
    align-items: center;
    gap: 12px;
    flex: 1;
}

.toggle-icon {
    font-size: 1.8rem;
}

.toggle-text {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.toggle-text strong {
    color: var(--text-primary);
    font-size: 1.1rem;
}

.toggle-description {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.exam-navigation {
    display: flex;
    gap: 15px;
    justify-content: space-between;
    margin-bottom: 30px;
    flex-wrap: wrap;
}

/* Question Palette */
.question-palette {
    background: var(--bg-secondary);
    padding: 20px;
    border-radius: 12px;
}

.question-palette h3 {
    font-size: 1rem;
    margin-bottom: 15px;
    color: var(--text-primary);
}

.palette-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(45px, 1fr));
    gap: 10px;
}

.palette-item {
    aspect-ratio: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: 8px;
    cursor: pointer;
    font-weight: 600;
    font-size: 0.9rem;
    transition: all 0.2s;
    color: var(--text-primary);
}

.palette-item:hover {
    transform: scale(1.1);
    border-color: var(--primary-color);
}

.palette-item.answered {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.palette-item.flagged {
    background: var(--warning-color);
    color: white;
    border-color: var(--warning-color);
}

.palette-item.current {
    border-width: 3px;
    border-color: var(--accent-color);
}

/* Results Screen */
.results-content {
    background: var(--bg-primary);
    border-radius: 20px;
    padding: 50px 40px;
    box-shadow: var(--shadow-lg);
    max-width: 800px;
    margin: 40px auto;
}

.results-header {
    text-align: center;
    margin-bottom: 40px;
}

.results-header h2 {
    font-size: 2rem;
    color: var(--secondary-color);
    margin-bottom: 30px;
}

.score-circle {
    position: relative;
    display: inline-block;
    margin-bottom: 20px;
}

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

.score-bg {
    fill: none;
    stroke: var(--bg-secondary);
    stroke-width: 12;
}

.score-fill {
    fill: none;
    stroke: var(--primary-color);
    stroke-width: 12;
    stroke-linecap: round;
    stroke-dasharray: 565.48;
    stroke-dashoffset: 565.48;
    transition: stroke-dashoffset 1s ease;
}

.score-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
}

#scorePercentage {
    display: block;
    font-size: 3rem;
    font-weight: 700;
    color: var(--primary-color);
}

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

.pass-status {
    padding: 12px 24px;
    border-radius: 25px;
    font-size: 1.1rem;
    font-weight: 600;
    display: inline-block;
}

.pass-status.passed {
    background: #e8f5e9;
    color: var(--success-color);
}

.pass-status.failed {
    background: #ffebee;
    color: var(--danger-color);
}

.results-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 20px;
    margin-bottom: 40px;
}

.stat-card {
    background: var(--bg-secondary);
    padding: 25px;
    border-radius: 12px;
    text-align: center;
}

.stat-value {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 5px;
}

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

.results-actions {
    display: flex;
    gap: 15px;
    justify-content: center;
    flex-wrap: wrap;
}

/* Review Screen */
#reviewScreen {
    background: var(--bg-primary);
    border-radius: 20px;
    padding: 30px;
    box-shadow: var(--shadow-lg);
}

.review-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 2px solid var(--border-color);
}

.review-header h2 {
    font-size: 1.8rem;
    color: var(--secondary-color);
}

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

.review-item {
    background: var(--bg-primary);
    padding: 30px;
    border-radius: 12px;
    margin-bottom: 25px;
    border-left: 5px solid var(--border-color);
}

.review-item.correct {
    border-left-color: var(--success-color);
}

.review-item.incorrect {
    border-left-color: var(--danger-color);
}

.review-question-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
}

.review-question-number {
    font-weight: 600;
    color: var(--text-primary);
}

.review-status {
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
}

.review-status.correct {
    background: #e8f5e9;
    color: var(--success-color);
}

.review-status.incorrect {
    background: #ffebee;
    color: var(--danger-color);
}

.review-question-text {
    font-size: 1.1rem;
    line-height: 1.6;
    margin-bottom: 20px;
    color: var(--text-primary);
}

.review-options {
    margin-bottom: 20px;
}

.review-option {
    padding: 12px 16px;
    margin-bottom: 10px;
    border-radius: 8px;
    border: 2px solid var(--border-color);
    background: var(--bg-secondary);
    color: var(--text-primary);
}

.review-option.user-answer {
    border-color: var(--accent-color);
    background: #e3f2fd;
}

.review-option.correct-answer {
    border-color: var(--success-color);
    background: #e8f5e9;
}

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

/* Dark mode overrides for review options */
body.dark-mode .review-option.user-answer {
    background: rgba(33, 150, 243, 0.2);
}

body.dark-mode .review-option.correct-answer {
    background: rgba(76, 175, 80, 0.2);
}

body.dark-mode .review-option.wrong-answer {
    background: rgba(239, 83, 80, 0.2);
}

.answer-label {
    display: inline-block;
    padding: 3px 10px;
    border-radius: 12px;
    font-size: 0.75rem;
    font-weight: 600;
    margin-left: 10px;
}

.answer-label.user {
    background: var(--accent-color);
    color: white;
}

.answer-label.correct {
    background: var(--success-color);
    color: white;
}

.explanation {
    background: var(--bg-secondary);
    padding: 20px;
    border-radius: 8px;
    border-left: 4px solid var(--accent-color);
}

.explanation-title {
    font-weight: 600;
    color: var(--accent-color);
    margin-bottom: 10px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.explanation-text {
    color: var(--text-primary);
    line-height: 1.6;
}

/* Responsive Design */
/* Dark Mode Toggle */
.dark-mode-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 1000;
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: 50px;
    padding: 10px 20px;
    cursor: pointer;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--text-primary);
}

.dark-mode-toggle:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.dark-mode-toggle .icon {
    font-size: 1.5rem;
    transition: transform 0.3s ease;
}

.dark-mode-toggle:hover .icon {
    transform: rotate(20deg);
}

@media (max-width: 768px) {
    body {
        padding: 10px;
    }

    .welcome-content {
        padding: 40px 20px;
    }

    .welcome-content h1 {
        font-size: 1.8rem;
    }

    .welcome-content h2 {
        font-size: 1.5rem;
    }

    #examScreen, #reviewScreen {
        padding: 20px;
    }

    .question-container {
        padding: 20px;
    }

    .question-text {
        font-size: 1.05rem;
    }

    .exam-navigation {
        gap: 10px;
    }

    .btn {
        padding: 12px 20px;
        font-size: 0.9rem;
    }

    .palette-grid {
        grid-template-columns: repeat(auto-fill, minmax(40px, 1fr));
        gap: 8px;
    }

    .results-content {
        padding: 30px 20px;
    }

    #scorePercentage {
        font-size: 2.5rem;
    }

    .dark-mode-toggle {
        padding: 8px 16px;
        font-size: 1rem;
    }

    .dark-mode-toggle .icon {
        font-size: 1.2rem;
    }
}

/* Exam Mode Selection */
.exam-modes {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin: 20px 0;
}

.exam-mode-card {
    background: var(--bg-secondary);
    padding: 30px 20px;
    border-radius: 12px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    border: 3px solid transparent;
}

.exam-mode-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
    background: var(--bg-primary);
}

.exam-mode-card.selected {
    border-color: var(--primary-color);
    background: rgba(255, 153, 0, 0.1);
}

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

.exam-mode-card h4 {
    color: var(--secondary-color);
    font-size: 1.3rem;
    margin-bottom: 10px;
}

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

/* Saved Exam Section */
.saved-exam-section {
    margin: 30px 0;
}

.saved-exam-alert {
    background: linear-gradient(135deg, #FFB84D 0%, #FF9900 100%);
    padding: 25px;
    border-radius: 15px;
    display: flex;
    align-items: center;
    gap: 20px;
    box-shadow: var(--shadow-lg);
    animation: slideIn 0.5s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.saved-exam-icon {
    font-size: 3rem;
}

.saved-exam-info {
    flex: 1;
}

.saved-exam-info h3 {
    color: #0f0f1e;
    font-size: 1.3rem;
    margin-bottom: 5px;
}

.saved-exam-info p {
    color: rgba(15, 15, 30, 0.8);
    font-size: 0.95rem;
}

.saved-exam-actions {
    display: flex;
    gap: 10px;
}

.saved-exam-actions .btn {
    min-width: 120px;
}

/* Config Screen */
.config-actions {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin-top: 30px;
}

.config-option {
    background: var(--bg-secondary);
    padding: 20px;
    border-radius: 10px;
    margin: 15px 0;
}

.config-option label {
    display: flex;
    align-items: center;
    gap: 15px;
    cursor: pointer;
    font-weight: 600;
    color: var(--text-primary);
}

.config-option input[type="checkbox"],
.config-option input[type="radio"] {
    width: 20px;
    height: 20px;
    cursor: pointer;
}

.config-option input[type="number"] {
    width: 100px;
    padding: 8px;
    border: 2px solid var(--border-color);
    border-radius: 6px;
    background: var(--bg-primary);
    color: var(--text-primary);
    font-size: 1rem;
}

.domain-list {
    display: grid;
    gap: 10px;
    margin-top: 15px;
}

.domain-item {
    background: var(--bg-secondary);
    padding: 15px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    gap: 12px;
    transition: all 0.2s ease;
}

.domain-item:hover {
    background: var(--bg-primary);
    box-shadow: var(--shadow);
}

.domain-item input[type="checkbox"] {
    width: 20px;
    height: 20px;
    cursor: pointer;
}

.domain-item label {
    flex: 1;
    cursor: pointer;
    font-weight: 500;
    color: var(--text-primary);
}

.domain-item .question-count {
    color: var(--text-secondary);
    font-size: 0.9rem;
    background: var(--primary-color);
    color: white;
    padding: 4px 12px;
    border-radius: 12px;
    font-weight: 600;
}

@media (max-width: 768px) {
    .saved-exam-alert {
        flex-direction: column;
        text-align: center;
    }

    .saved-exam-actions {
        width: 100%;
        flex-direction: column;
    }

    .saved-exam-actions .btn {
        width: 100%;
    }

    .exam-modes {
        grid-template-columns: 1fr;
    }
}