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

:root {
    --primary-color: #ff9900;
    --primary-dark: #e68900;
    --secondary-color: #232f3e;
    --background: #f5f5f5;
    --card-background: #ffffff;
    --text-primary: #232f3e;
    --text-secondary: #666666;
    --text-light: #999999;
    --border-color: #e0e0e0;
    --success-color: #22c55e;
    --error-color: #ef4444;
    --info-color: #3b82f6;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.1);
    --border-radius: 12px;
    --transition: all 0.3s ease;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    padding: 20px;
    min-height: 100vh;
}

.container {
    max-width: 1000px;
    margin: 0 auto;
}

.container.hidden {
    display: none;
}

/* Exam Selection Screen */
.exam-selection-screen {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
    background: var(--background);
}

.exam-selection-screen.hidden {
    display: none;
}

.exam-selection-container {
    max-width: 1200px;
    width: 100%;
}

.exam-selection-header {
    text-align: center;
    margin-bottom: 50px;
}

.exam-selection-header h1 {
    font-size: 42px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 10px;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.exam-selection-subtitle {
    font-size: 18px;
    color: var(--text-secondary);
    font-weight: 400;
}

.exam-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 25px;
    margin-top: 40px;
}

.exam-card {
    background: var(--card-background);
    border-radius: var(--border-radius);
    padding: 30px;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
    cursor: pointer;
    border: 2px solid transparent;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

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

.exam-card:focus-visible {
    outline: 3px solid var(--primary-color);
    outline-offset: 2px;
}

.exam-card-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 15px;
    padding-bottom: 15px;
    border-bottom: 2px solid var(--border-color);
}

.exam-card-title {
    font-size: 20px;
    font-weight: 600;
    color: var(--text-primary);
    margin: 0;
    flex: 1;
    line-height: 1.4;
}

.exam-card-code {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 6px 12px;
    border-radius: 6px;
    font-size: 14px;
    font-weight: 600;
    white-space: nowrap;
}

.exam-card-body {
    flex: 1;
}

.exam-card-info {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.exam-info-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.exam-info-label {
    font-size: 14px;
    color: var(--text-secondary);
    font-weight: 500;
}

.exam-info-value {
    font-size: 15px;
    color: var(--text-primary);
    font-weight: 600;
}

.exam-card-footer {
    padding-top: 15px;
    border-top: 2px solid var(--border-color);
}

.btn-start-exam {
    width: 100%;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    border: none;
    padding: 14px 24px;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

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

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

.btn-start-exam:focus-visible {
    outline: 3px solid var(--primary-color);
    outline-offset: 2px;
}

.exam-loading,
.exam-error {
    grid-column: 1 / -1;
    text-align: center;
    padding: 60px 20px;
    color: var(--text-secondary);
    font-size: 18px;
}

.exam-error {
    color: var(--error-color);
}

/* Header Styles */
.header {
    background: linear-gradient(135deg, var(--secondary-color) 0%, #1a1f2e 100%);
    color: white;
    padding: 30px 40px;
    border-radius: var(--border-radius);
    margin-bottom: 30px;
    box-shadow: var(--shadow-lg);
    position: relative;
}

.header-content h1 {
    font-size: 28px;
    font-weight: 600;
    margin-bottom: 8px;
}

.exam-code {
    font-size: 18px;
    opacity: 0.9;
    font-weight: 500;
}

.question-range {
    font-size: 16px;
    opacity: 0.85;
    font-weight: 400;
    margin-top: 4px;
}

/* Header Actions */
.header-actions {
    margin-top: 15px;
    display: flex;
    gap: 15px;
    align-items: center;
    flex-wrap: wrap;
}

/* Score Display */
.score-display {
    padding: 12px 20px;
    background: rgba(255, 255, 255, 0.15);
    border-radius: 8px;
    display: inline-flex;
    align-items: center;
    gap: 10px;
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.score-display.hidden {
    display: none;
}

.score-label {
    font-size: 15px;
    font-weight: 500;
    opacity: 0.9;
}

.score-value {
    font-size: 18px;
    font-weight: 700;
    background: rgba(255, 255, 255, 0.2);
    padding: 6px 14px;
    border-radius: 6px;
    min-width: 80px;
    text-align: center;
}

#score-correct {
    color: #4ade80;
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.2);
}

#score-total {
    opacity: 0.95;
}

/* Review Button */
.btn-back-to-selection {
    background: linear-gradient(135deg, #6b7280 0%, #4b5563 100%);
    color: white;
    border: none;
    padding: 12px 20px;
    font-size: 15px;
    font-weight: 600;
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-md);
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.btn-back-to-selection.header-top-right {
    position: absolute;
    top: 20px;
    right: 20px;
    z-index: 10;
}

.btn-back-to-selection:hover {
    background: linear-gradient(135deg, #4b5563 0%, #374151 100%);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-back-to-selection:active {
    transform: translateY(0);
}

.btn-back-to-selection:focus-visible {
    outline: 3px solid #6b7280;
    outline-offset: 2px;
}

.btn-review {
    background: linear-gradient(135deg, #3b82f6 0%, #2563eb 100%);
    color: white;
    border: none;
    padding: 12px 24px;
    font-size: 15px;
    font-weight: 600;
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-md);
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.btn-review:hover {
    background: linear-gradient(135deg, #2563eb 0%, #1d4ed8 100%);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

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

.btn-review:focus-visible {
    outline: 3px solid #3b82f6;
    outline-offset: 2px;
}

/* Review Modal */
.review-modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(5px);
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
    animation: fadeIn 0.3s ease;
}

.review-modal.hidden {
    display: none;
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

.review-modal-content {
    background: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    max-width: 900px;
    width: 100%;
    max-height: 90vh;
    display: flex;
    flex-direction: column;
    animation: slideUp 0.3s ease;
}

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

.review-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 25px 30px;
    border-bottom: 2px solid var(--border-color);
}

.review-header h2 {
    font-size: 24px;
    font-weight: 600;
    color: var(--text-primary);
    margin: 0;
}

.review-header-actions {
    display: flex;
    align-items: center;
    gap: 15px;
}

.btn-clear-all {
    background: linear-gradient(135deg, #ef4444 0%, #dc2626 100%);
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

.btn-clear-all:hover {
    background: linear-gradient(135deg, #dc2626 0%, #b91c1c 100%);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

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

.btn-clear-all:focus-visible {
    outline: 3px solid #ef4444;
    outline-offset: 2px;
}

.review-close {
    background: none;
    border: none;
    font-size: 32px;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 0;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    transition: var(--transition);
}

.review-close:hover {
    background: var(--background);
    color: var(--text-primary);
}

.review-stats {
    display: flex;
    gap: 20px;
    padding: 20px 30px;
    background: var(--background);
    border-bottom: 2px solid var(--border-color);
}

.stat-item {
    display: flex;
    flex-direction: column;
    gap: 5px;
}

.stat-label {
    font-size: 13px;
    color: var(--text-secondary);
    font-weight: 500;
}

.stat-value {
    font-size: 24px;
    font-weight: 700;
    color: var(--text-primary);
}

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

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

.review-list {
    padding: 20px 30px;
    overflow-y: auto;
    flex: 1;
}

.review-empty {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-secondary);
}

.review-empty p {
    margin: 10px 0;
    font-size: 16px;
}

.review-item {
    display: flex;
    gap: 15px;
    padding: 18px;
    margin-bottom: 12px;
    background: var(--card-background);
    border: 2px solid var(--border-color);
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
}

.review-item:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
    transform: translateX(4px);
}

.review-item.correct {
    border-left: 4px solid var(--success-color);
}

.review-item.wrong {
    border-left: 4px solid var(--error-color);
}

.review-item-icon {
    font-size: 28px;
    font-weight: bold;
    flex-shrink: 0;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    background: var(--background);
}

.review-item.correct .review-item-icon {
    color: var(--success-color);
    background: #f0fdf4;
}

.review-item.wrong .review-item-icon {
    color: var(--error-color);
    background: #fef2f2;
}

.review-item-content {
    flex: 1;
    min-width: 0;
}

.review-item-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 8px;
}

.review-item-number {
    font-size: 16px;
    font-weight: 600;
    color: var(--text-primary);
}

.review-item-status {
    font-size: 13px;
    font-weight: 600;
    padding: 4px 12px;
    border-radius: 6px;
}

.review-item.correct .review-item-status {
    background: #f0fdf4;
    color: var(--success-color);
}

.review-item.wrong .review-item-status {
    background: #fef2f2;
    color: var(--error-color);
}

.review-item-preview {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 10px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.review-item-answers {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 14px;
    flex-wrap: wrap;
}

.review-answer-label {
    color: var(--text-secondary);
    font-weight: 500;
}

.review-answer-value {
    font-weight: 700;
    padding: 4px 10px;
    border-radius: 4px;
}

.review-answer-value.correct {
    background: #f0fdf4;
    color: var(--success-color);
}

.review-answer-value.wrong {
    background: #fef2f2;
    color: var(--error-color);
}

.review-answer-separator {
    color: var(--text-light);
    margin: 0 4px;
}

/* Main Content */
.main-content {
    background: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    padding: 40px;
    margin-bottom: 30px;
}

/* Question Header */
.question-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 25px;
    padding-bottom: 15px;
    border-bottom: 2px solid var(--border-color);
}

.question-number {
    font-size: 18px;
    font-weight: 600;
    color: var(--text-primary);
}

.question-topic {
    font-size: 14px;
    color: var(--text-secondary);
    background: var(--background);
    padding: 6px 12px;
    border-radius: 6px;
}

/* Question Text */
.question-text {
    font-size: 17px;
    line-height: 1.8;
    color: var(--text-primary);
    margin-bottom: 30px;
    padding: 20px;
    background: var(--background);
    border-radius: 8px;
    border-left: 4px solid var(--primary-color);
}

/* Options Container */
.options-container {
    margin-bottom: 30px;
}

.option-item {
    padding: 18px 20px;
    margin-bottom: 12px;
    background: var(--card-background);
    border: 2px solid var(--border-color);
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
    font-size: 15px;
    line-height: 1.6;
}

.option-item:hover {
    border-color: var(--primary-color);
    background: #fff9f0;
    transform: translateX(4px);
}

.option-item.selected {
    border-color: var(--primary-color);
    background: #fff9f0;
    box-shadow: 0 2px 8px rgba(255, 153, 0, 0.2);
}

.option-item.correct {
    border-color: var(--success-color);
    background: #f0fdf4;
    box-shadow: 0 2px 8px rgba(34, 197, 94, 0.2);
}

.option-item.wrong {
    border-color: var(--error-color);
    background: #fef2f2;
    box-shadow: 0 2px 8px rgba(239, 68, 68, 0.2);
}

.option-item.correct.selected {
    border-width: 3px;
}

.option-item.wrong.selected {
    border-width: 3px;
}

.option-item {
    position: relative;
    display: flex;
    align-items: center;
}

.option-text {
    flex: 1;
}

.option-icon {
    margin-left: auto;
    font-size: 20px;
    font-weight: bold;
    padding-left: 12px;
}

.option-item.correct .option-icon {
    color: var(--success-color);
}

.option-item.wrong .option-icon {
    color: var(--error-color);
}

.option-label {
    font-weight: 600;
    color: var(--primary-color);
    margin-right: 12px;
    display: inline-block;
    min-width: 30px;
}

.option-item.correct .option-label {
    color: var(--success-color);
}

.option-item.wrong .option-label {
    color: var(--error-color);
}

/* Answer Feedback */
.answer-feedback {
    margin: 20px 0;
    padding: 16px 20px;
    border-radius: 8px;
    animation: slideDown 0.3s ease;
}

.answer-feedback.correct {
    background: #f0fdf4;
    border: 2px solid var(--success-color);
}

.answer-feedback.wrong {
    background: #fef2f2;
    border: 2px solid var(--error-color);
}

.feedback-content {
    display: flex;
    align-items: center;
    gap: 12px;
}

.feedback-icon {
    font-size: 24px;
    font-weight: bold;
    flex-shrink: 0;
}

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

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

.feedback-text {
    font-size: 16px;
    font-weight: 500;
    color: var(--text-primary);
}

/* Action Section */
.action-section {
    margin: 30px 0;
    text-align: center;
    display: flex;
    gap: 15px;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
}

.btn-show-answer {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    border: none;
    padding: 16px 40px;
    font-size: 16px;
    font-weight: 600;
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-md);
    display: inline-flex;
    align-items: center;
    gap: 10px;
}

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

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

.btn-show-answer.expanded .btn-icon {
    transform: rotate(180deg);
}

.btn-icon {
    transition: transform 0.3s ease;
    font-size: 12px;
}

.btn-check-answer {
    background: linear-gradient(135deg, var(--success-color) 0%, #16a34a 100%);
    color: white;
    border: none;
    padding: 16px 40px;
    font-size: 16px;
    font-weight: 600;
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-md);
    display: inline-flex;
    align-items: center;
    gap: 10px;
}

.btn-check-answer:hover {
    background: linear-gradient(135deg, #16a34a 0%, #15803d 100%);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

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

.btn-check-answer:focus-visible {
    outline: 3px solid var(--success-color);
    outline-offset: 2px;
}

.btn-clear-answer {
    background: linear-gradient(135deg, #6b7280 0%, #4b5563 100%);
    color: white;
    border: none;
    padding: 16px 40px;
    font-size: 16px;
    font-weight: 600;
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-md);
    display: inline-flex;
    align-items: center;
    gap: 10px;
}

.btn-clear-answer:hover {
    background: linear-gradient(135deg, #4b5563 0%, #374151 100%);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

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

.btn-clear-answer:focus-visible {
    outline: 3px solid #6b7280;
    outline-offset: 2px;
}

/* Answer Section */
.answer-section {
    margin-top: 30px;
    padding: 25px;
    background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
    border-radius: var(--border-radius);
    border: 2px solid var(--info-color);
    animation: slideDown 0.3s ease;
}

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

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

.answer-header h3 {
    font-size: 20px;
    color: var(--text-primary);
    font-weight: 600;
}

.answer-badge {
    background: var(--success-color);
    color: white;
    padding: 8px 16px;
    border-radius: 6px;
    font-size: 18px;
    font-weight: 700;
    box-shadow: var(--shadow-sm);
}

/* Vote Distribution */
.vote-distribution {
    margin-top: 15px;
}

.vote-item {
    margin-bottom: 12px;
}

.vote-label {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 6px;
    font-size: 14px;
    font-weight: 500;
}

.vote-bar-container {
    height: 28px;
    background: #e5e7eb;
    border-radius: 6px;
    overflow: hidden;
    position: relative;
}

.vote-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--info-color) 0%, #60a5fa 100%);
    border-radius: 6px;
    transition: width 0.6s ease;
    display: flex;
    align-items: center;
    padding: 0 10px;
    color: white;
    font-size: 13px;
    font-weight: 600;
}

.vote-bar.highest {
    background: linear-gradient(90deg, var(--success-color) 0%, #4ade80 100%);
}

/* Comments Section */
.comments-section {
    margin-top: 30px;
    animation: slideDown 0.3s ease;
}

.comments-title {
    font-size: 20px;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 20px;
    padding-bottom: 10px;
    border-bottom: 2px solid var(--border-color);
}

.comments-list {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.comment-card {
    background: var(--card-background);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 20px;
    transition: var(--transition);
}

.comment-card:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
}

.comment-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 12px;
}

.comment-answer {
    background: var(--primary-color);
    color: white;
    padding: 4px 12px;
    border-radius: 6px;
    font-size: 14px;
    font-weight: 600;
}

.comment-upvotes {
    display: flex;
    align-items: center;
    gap: 6px;
    color: var(--text-secondary);
    font-size: 14px;
    font-weight: 500;
}

.upvote-icon {
    color: var(--success-color);
    font-size: 16px;
}

.comment-explanation {
    color: var(--text-primary);
    line-height: 1.7;
    font-size: 15px;
    white-space: pre-wrap;
}

/* Navigation */
.navigation {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--card-background);
    padding: 20px 40px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
}

.btn-nav {
    background: var(--secondary-color);
    color: white;
    border: none;
    padding: 12px 24px;
    font-size: 15px;
    font-weight: 500;
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
}

.btn-nav:hover:not(:disabled) {
    background: #1a1f2e;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

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

.btn-nav:focus-visible,
.btn-go:focus-visible,
.btn-show-answer:focus-visible {
    outline: 3px solid var(--primary-color);
    outline-offset: 2px;
}

.question-counter {
    font-size: 16px;
    font-weight: 600;
    color: var(--text-primary);
}

/* Question Jump */
.question-jump {
    display: flex;
    align-items: center;
    gap: 8px;
}

.jump-label {
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
    white-space: nowrap;
}

.question-input {
    width: 80px;
    padding: 10px 12px;
    font-size: 15px;
    font-weight: 500;
    border: 2px solid var(--border-color);
    border-radius: 6px;
    text-align: center;
    transition: var(--transition);
    background: var(--card-background);
    color: var(--text-primary);
}

.question-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(255, 153, 0, 0.1);
}

.question-input:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

.question-input:invalid {
    border-color: var(--error-color);
}

.question-input::placeholder {
    color: var(--text-light);
}

.btn-go {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 10px 20px;
    font-size: 14px;
    font-weight: 600;
    border-radius: 6px;
    cursor: pointer;
    transition: var(--transition);
    white-space: nowrap;
}

.btn-go:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

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

/* Utility Classes */
.hidden {
    display: none;
}

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

    .exam-selection-header h1 {
        font-size: 32px;
    }

    .exam-selection-subtitle {
        font-size: 16px;
    }

    .exam-list {
        grid-template-columns: 1fr;
        gap: 20px;
        margin-top: 30px;
    }

    .exam-card {
        padding: 20px;
    }

    .exam-card-header {
        flex-direction: column;
        align-items: flex-start;
    }

    .exam-card-code {
        align-self: flex-start;
    }

    .header {
        padding: 20px 25px;
        padding-top: 60px;
    }

    .btn-back-to-selection.header-top-right {
        top: 15px;
        right: 15px;
        padding: 10px 16px;
        font-size: 14px;
    }

    .header-content h1 {
        font-size: 22px;
    }

    .exam-code {
        font-size: 16px;
    }

    .question-range {
        font-size: 14px;
    }

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

    .score-display {
        padding: 10px 16px;
        flex-direction: column;
        gap: 8px;
        width: 100%;
    }

    .btn-review {
        width: 100%;
        justify-content: center;
    }

    .review-modal-content {
        max-height: 95vh;
    }

    .review-header {
        padding: 20px;
        flex-wrap: wrap;
        gap: 15px;
    }

    .review-header h2 {
        font-size: 20px;
    }

    .review-header-actions {
        gap: 10px;
    }

    .btn-clear-all {
        padding: 8px 16px;
        font-size: 13px;
    }

    .review-stats {
        flex-direction: column;
        gap: 15px;
        padding: 15px 20px;
    }

    .review-list {
        padding: 15px 20px;
    }

    .review-item {
        flex-direction: column;
        gap: 12px;
    }

    .review-item-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 8px;
    }

    .score-label {
        font-size: 14px;
    }

    .score-value {
        font-size: 16px;
        width: 100%;
    }

    .main-content {
        padding: 25px 20px;
    }

    .question-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 10px;
    }

    .question-text {
        font-size: 16px;
        padding: 15px;
    }

    .option-item {
        padding: 15px;
        font-size: 14px;
    }

    .action-section {
        flex-direction: column;
    }

    .btn-show-answer,
    .btn-check-answer,
    .btn-clear-answer {
        width: 100%;
        justify-content: center;
        padding: 14px 30px;
    }

    .answer-section {
        padding: 20px;
    }

    .navigation {
        flex-direction: column;
        gap: 15px;
        padding: 20px;
    }

    .btn-nav {
        width: 100%;
    }

    .question-jump {
        width: 100%;
        justify-content: center;
    }

    .question-input {
        flex: 1;
        max-width: 120px;
    }

    .question-counter {
        order: -1;
    }
}

@media (max-width: 480px) {
    .exam-selection-header h1 {
        font-size: 28px;
    }

    .exam-selection-subtitle {
        font-size: 14px;
    }

    .exam-card {
        padding: 15px;
    }

    .exam-card-title {
        font-size: 18px;
    }

    .header {
        padding-top: 55px;
    }

    .btn-back-to-selection.header-top-right {
        top: 10px;
        right: 10px;
        padding: 8px 12px;
        font-size: 13px;
    }

    .header-content h1 {
        font-size: 18px;
    }

    .question-text {
        font-size: 15px;
    }

    .option-item {
        padding: 12px;
        font-size: 13px;
    }

    .comment-card {
        padding: 15px;
    }
}