/* 기존 CSS 내용 + 추가 스타일들 */

/* 메인 컨테이너 스타일 */
.learning-container {
    padding: 20px;
    padding-bottom: 120px; /* 하단 여백 추가 */
    max-width: 1400px;
    margin: 0 auto;
}

.split-layout {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 30px;
    margin-top: 20px;
}

.theory-panel {
    background: white;
    border-radius: 12px;
    padding: 30px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    height: fit-content;
    position: sticky;
    top: 20px;
}

.practice-panel {
    background: white;
    border-radius: 12px;
    padding: 30px;
    padding-bottom: 100px; /* 아래쪽 패딩 추가 */
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    display: flex;
    flex-direction: column;
    min-height: 80vh;
}

/* 프로그레스 바 스타일 */
.progress-indicator {
    margin-bottom: 25px;
    text-align: center;
}

.progress-bar {
    width: 100%;
    height: 8px;
    background: #e0e0e0;
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 10px;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, #FF6B35, #F7931E);
    transition: width 0.3s ease;
}

.progress-text {
    font-size: 14px;
    color: #6c757d;
    font-weight: 500;
}

/* 레슨 헤더 스타일 */
.lesson-header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    padding: 25px 30px;
    border-radius: 15px;
    margin-bottom: 25px;
    text-align: center;
    position: relative;
    overflow: hidden;
    box-shadow: 0 8px 25px rgba(102, 126, 234, 0.3);
}

.lesson-header::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -10%;
    width: 200px;
    height: 200px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 50%;
    z-index: 1;
}

.lesson-header::after {
    content: '';
    position: absolute;
    bottom: -50%;
    left: -10%;
    width: 150px;
    height: 150px;
    background: rgba(255, 255, 255, 0.08);
    border-radius: 50%;
    z-index: 1;
}

.lesson-header h2 {
    color: white;
    margin: 0;
    font-size: 32px;
    font-weight: 700;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
    z-index: 2;
    position: relative;
    letter-spacing: -0.5px;
}

/* 조건문 관련 스타일 */
.conditional-overview {
    background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);
    padding: 20px;
    border-radius: 12px;
    margin-bottom: 20px;
}

.conditional-timeline {
    display: flex;
    justify-content: space-around;
    margin-top: 15px;
    gap: 10px;
}

.conditional-item {
    text-align: center;
    padding: 15px;
    border-radius: 10px;
    flex: 1;
}

.conditional-item.zero { background: linear-gradient(135deg, #17a2b8, #20c997); color: white; }
.conditional-item.first { background: linear-gradient(135deg, #007bff, #6f42c1); color: white; }
.conditional-item.second { background: linear-gradient(135deg, #fd7e14, #e83e8c); color: white; }

.conditional-icon {
    font-size: 24px;
    margin-bottom: 8px;
}

.conditional-details .conditional-section {
    background: white;
    padding: 20px;
    margin: 15px 0;
    border-radius: 10px;
    border-left: 4px solid #FF9800;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.conditional-formula {
    background: #f8f9fa;
    padding: 10px;
    border-radius: 6px;
    margin: 10px 0;
    font-family: monospace;
}

/* 조동사 관련 스타일 */
.modal-overview {
    background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);
    padding: 20px;
    border-radius: 12px;
    margin-bottom: 20px;
}

.modal-timeline {
    display: flex;
    justify-content: space-around;
    margin-top: 15px;
    gap: 10px;
}

.modal-item {
    text-align: center;
    padding: 15px;
    border-radius: 10px;
    flex: 1;
}

.modal-item.can { background: linear-gradient(135deg, #28a745, #20c997); color: white; }
.modal-item.will { background: linear-gradient(135deg, #007bff, #6610f2); color: white; }
.modal-item.must { background: linear-gradient(135deg, #dc3545, #fd7e14); color: white; }

.modal-icon {
    font-size: 24px;
    margin-bottom: 8px;
}

.modal-details .modal-section {
    background: white;
    padding: 20px;
    margin: 15px 0;
    border-radius: 10px;
    border-left: 4px solid #2196F3;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.modal-formula {
    background: #f8f9fa;
    padding: 10px;
    border-radius: 6px;
    margin: 10px 0;
    font-family: monospace;
}

/* 시제 관련 스타일 */
.tense-overview {
    background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);
    padding: 20px;
    border-radius: 12px;
    margin-bottom: 20px;
}

.tense-timeline {
    display: flex;
    justify-content: space-around;
    margin-top: 15px;
    gap: 10px;
}

.tense-item {
    text-align: center;
    padding: 15px;
    border-radius: 10px;
    flex: 1;
}

.tense-item.past { background: linear-gradient(135deg, #FF6B6B, #FF8E8E); color: white; }
.tense-item.present { background: linear-gradient(135deg, #4ECDC4, #44A08D); color: white; }
.tense-item.future { background: linear-gradient(135deg, #45B7D1, #96C5F7); color: white; }

.tense-icon {
    font-size: 24px;
    margin-bottom: 8px;
}

.tense-details .tense-section {
    background: white;
    padding: 20px;
    margin: 15px 0;
    border-radius: 10px;
    border-left: 4px solid #007bff;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.tense-formula {
    background: #f8f9fa;
    padding: 10px;
    border-radius: 6px;
    margin: 10px 0;
    font-family: monospace;
}

.example-box {
    background: #e8f5e8;
    padding: 15px;
    border-radius: 8px;
    margin: 10px 0;
}

.usage-tip {
    background: #fff3cd;
    padding: 10px;
    border-radius: 6px;
    margin-top: 10px;
    border-left: 3px solid #ffc107;
}

.quick-reference {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 20px;
    border-radius: 12px;
    margin-top: 20px;
}

.reference-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 10px;
    margin-top: 15px;
}

.ref-item {
    background: rgba(255,255,255,0.2);
    padding: 10px;
    border-radius: 6px;
    text-align: center;
}

/* 퀴즈 관련 추가 스타일 */
.question-card {
    background: white;
    padding: 25px;
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    margin-bottom: 20px;
}

.question-number {
    background: #007bff;
    color: white;
    padding: 5px 12px;
    border-radius: 15px;
    font-size: 12px;
    display: inline-block;
    margin-bottom: 15px;
}

.question-text {
    margin-bottom: 20px;
    color: #333;
    line-height: 1.5;
}

.fill-container, .translation-container {
    margin-bottom: 20px;
}

.fill-input, .translation-input {
    width: 100%;
    padding: 12px;
    border: 2px solid #e9ecef;
    border-radius: 8px;
    font-size: 16px;
    transition: border-color 0.3s ease;
}

.fill-input:focus, .translation-input:focus {
    outline: none;
    border-color: #007bff;
}

.translation-input {
    resize: vertical;
    min-height: 80px;
}

.hint-options {
    color: #6c757d;
    font-size: 14px;
    margin-top: 8px;
}

.word-order-container {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 15px;
    padding: 15px;
    background: #f8f9fa;
    border-radius: 8px;
}

.word-tile {
    background: #007bff;
    color: white;
    padding: 8px 12px;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.3s ease;
    user-select: none;
}

.word-tile:hover {
    background: #0056b3;
    transform: translateY(-2px);
}

.word-tile.selected {
    background: #28a745;
}

.sentence-builder {
    min-height: 50px;
    padding: 15px;
    border: 2px dashed #dee2e6;
    border-radius: 8px;
    display: flex;
    flex-wrap: wrap;
    gap: 5px;
    align-items: center;
    margin-bottom: 20px;
}

.check-btn {
    background: #28a745;
    color: white;
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 16px;
    transition: background 0.3s ease;
}

.check-btn:hover {
    background: #218838;
}

.explanation {
    margin-top: 20px;
    padding: 15px;
    border-radius: 8px;
    display: flex;
    align-items: flex-start;
    gap: 12px;
}

.explanation.correct {
    background: #d4edda;
    border: 1px solid #c3e6cb;
    color: #155724;
}

.explanation.incorrect {
    background: #f8d7da;
    border: 1px solid #f5c6cb;
    color: #721c24;
}

.result-icon {
    font-size: 24px;
    margin-top: 2px;
}

.final-score {
    text-align: center;
    padding: 40px;
}

.score-circle {
    width: 120px;
    height: 120px;
    border-radius: 50%;
    background: linear-gradient(135deg, #007bff, #0056b3);
    color: white;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    margin: 0 auto 20px;
}

.score-number {
    font-size: 36px;
    font-weight: bold;
}

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

.score-message {
    font-size: 18px;
    margin: 20px 0;
}

/* 주제 선택기 추가 스타일 */
.topic-selector {
    display: none;
    opacity: 0;
    transform: translateY(-20px);
    transition: all 0.3s ease;
    background: white;
    padding: 20px;
    border-radius: 12px;
    box-shadow: 0 8px 24px rgba(0,0,0,0.1);
    margin-bottom: 20px;
}

.topic-selector.visible {
    opacity: 1;
    transform: translateY(0);
}

.topic-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 15px;
}

.topic-card {
    background: white;
    border: 2px solid #e9ecef;
    border-radius: 10px;
    padding: 15px;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
    display: flex;
    align-items: center;
    gap: 15px;
}

.topic-card:hover {
    border-color: #007bff;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.topic-card.current {
    border-color: #28a745;
    background: linear-gradient(135deg, #d4edda 0%, #c3e6cb 100%);
}

.topic-card.unavailable {
    opacity: 0.6;
    cursor: not-allowed;
}

.topic-card.unavailable .lock-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(255,255,255,0.8);
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    font-size: 24px;
    color: #6c757d;
}

.topic-icon {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 20px;
    flex-shrink: 0;
}

.topic-info h4 {
    margin: 0 0 5px 0;
    color: #333;
    font-size: 16px;
}

.topic-info p {
    margin: 0;
    color: #6c757d;
    font-size: 14px;
}

.current-badge {
    position: absolute;
    top: 8px;
    right: 8px;
    background: #28a745;
    color: white;
    padding: 2px 8px;
    border-radius: 10px;
    font-size: 10px;
    font-weight: bold;
}

/* 모달 스타일 */
.coming-soon-modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0,0,0,0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.coming-soon-modal.visible {
    opacity: 1;
}

.modal-content {
    background: white;
    padding: 30px;
    border-radius: 12px;
    text-align: center;
    max-width: 400px;
    width: 90%;
    transform: scale(0.8);
    transition: transform 0.3s ease;
}

.coming-soon-modal.visible .modal-content {
    transform: scale(1);
}

.modal-icon {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 20px;
    color: white;
    font-size: 32px;
}

.modal-content h3 {
    margin: 10px 0;
    color: #333;
}

.modal-content p {
    color: #6c757d;
    margin: 10px 0;
}

.subtitle {
    font-style: italic;
    font-size: 14px;
}

.toggle-icon {
    transition: transform 0.3s ease;
}

/* 백 헤더 스타일 */
.back-header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    padding: 20px;
    border-radius: 15px;
    margin-bottom: 25px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    box-shadow: 0 8px 25px rgba(102, 126, 234, 0.3);
    position: relative;
    overflow: hidden;
}

.back-header::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -20px;
    width: 200px;
    height: 200px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 50%;
    z-index: 1;
}

.back-header::after {
    content: '';
    position: absolute;
    bottom: -30%;
    left: -30px;
    width: 150px;
    height: 150px;
    background: rgba(255, 255, 255, 0.08);
    border-radius: 50%;
    z-index: 1;
}

.back-button {
    background: rgba(255, 255, 255, 0.2);
    color: white;
    width: 45px;
    height: 45px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    transition: all 0.3s ease;
    border: 2px solid rgba(255, 255, 255, 0.3);
    backdrop-filter: blur(10px);
    z-index: 2;
    position: relative;
}

.back-button:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
}

.back-button i {
    font-size: 18px;
}

.back-header h1 {
    color: white;
    margin: 0;
    font-size: 28px;
    font-weight: 700;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
    z-index: 2;
    position: relative;
    flex: 1;
    text-align: center;
}

.level-indicator {
    background: rgba(255, 255, 255, 0.25);
    color: white;
    padding: 8px 16px;
    border-radius: 25px;
    font-size: 14px;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 8px;
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.3);
    z-index: 2;
    position: relative;
}

.level-indicator i {
    color: #FFD700;
    text-shadow: 0 0 10px rgba(255, 215, 0, 0.5);
}

/* 토픽 토글 버튼 개선 */
.topic-toggle-container {
    margin-bottom: 25px;
}

.topic-toggle-btn {
    background: linear-gradient(135deg, #FF6B35 0%, #F7931E 100%);
    color: white;
    border: none;
    padding: 15px 30px;
    border-radius: 10px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    transition: all 0.3s ease;
    box-shadow: 0 6px 20px rgba(255, 107, 53, 0.3);
    position: relative;
    overflow: hidden;
}

.topic-toggle-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(255, 107, 53, 0.4);
}

.topic-toggle-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

.topic-toggle-btn:hover::before {
    left: 100%;
}

.topic-toggle-btn i:first-child {
    font-size: 18px;
}

.toggle-icon {
    transition: transform 0.3s ease;
    font-size: 14px;
}

/* 퀴즈 세트 스타일 */
.question-set {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.set-header {
    text-align: center;
    background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);
    padding: 20px;
    border-radius: 12px;
    margin-bottom: 10px;
}

.set-header h3 {
    margin: 0 0 5px 0;
    color: #2c3e50;
    font-size: 24px;
}

.set-header p {
    margin: 0;
    color: #6c757d;
    font-size: 16px;
}

.set-controls {
    text-align: center;
    margin-top: 20px;
    padding: 20px;
    background: #f8f9fa;
    border-radius: 12px;
}

.set-result {
    text-align: center;
}

.set-result h4 {
    color: #2c3e50;
    margin-bottom: 10px;
    font-size: 20px;
}

.set-result p {
    color: #6c757d;
    margin-bottom: 15px;
    font-size: 16px;
}

.result-buttons {
    display: flex;
    justify-content: center;
    gap: 15px;
}

.score-breakdown {
    background: #f8f9fa;
    padding: 15px;
    border-radius: 8px;
    margin: 15px 0;
    color: #6c757d;
}

/* 퀴즈 카드 개선 */
.question-card {
    background: white;
    padding: 30px;
    border-radius: 20px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    margin-bottom: 25px;
    border: 1px solid rgba(0, 0, 0, 0.05);
    position: relative;
    overflow: hidden;
}

.question-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, #FF6B35, #F7931E, #667eea, #764ba2);
}

.question-number {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 8px 16px;
    border-radius: 20px;
    font-size: 14px;
    font-weight: 600;
    display: inline-block;
    margin-bottom: 20px;
    box-shadow: 0 4px 12px rgba(102, 126, 234, 0.3);
}

.question-text {
    margin-bottom: 25px;
    color: #2c3e50;
    line-height: 1.6;
    font-size: 18px;
    font-weight: 500;
}

.options-container {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-bottom: 25px;
}

.option-label {
    display: flex;
    align-items: center;
    padding: 16px 20px;
    border: 2px solid #e9ecef;
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.3s ease;
    background: #fdfdfd;
    position: relative;
    overflow: hidden;
}

.option-label::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 107, 53, 0.1), transparent);
    transition: left 0.5s;
}

.option-label:hover {
    border-color: #FF6B35;
    background: #fff8f6;
    transform: translateX(5px);
    box-shadow: 0 4px 15px rgba(255, 107, 53, 0.2);
}

.option-label:hover::before {
    left: 100%;
}

.option-label input[type="radio"] {
    margin-right: 15px;
    width: 20px;
    height: 20px;
    accent-color: #FF6B35;
}

.option-text {
    font-size: 16px;
    color: #2c3e50;
    line-height: 1.4;
}

.check-btn {
    background: linear-gradient(135deg, #28a745 0%, #20c997 100%);
    color: white;
    padding: 14px 28px;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    font-size: 16px;
    font-weight: 600;
    transition: all 0.3s ease;
    box-shadow: 0 6px 20px rgba(40, 167, 69, 0.3);
    position: relative;
    overflow: hidden;
}

.check-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

.check-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(40, 167, 69, 0.4);
}

.check-btn:hover::before {
    left: 100%;
}

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

/* 이론 섹션 스타일 */
.theory-section {
    background: white;
    padding: 20px;
    margin: 15px 0;
    border-radius: 10px;
    border-left: 4px solid #2196F3;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.theory-content {
    margin-top: 15px;
}

/* 동사 테이블 스타일 */
.verb-table {
    display: flex;
    flex-direction: column;
    gap: 10px;
    margin: 15px 0;
}

.verb-row {
    display: grid;
    grid-template-columns: 80px 100px 1fr;
    gap: 15px;
    align-items: center;
    padding: 12px;
    background: #f8f9fa;
    border-radius: 8px;
    border-left: 3px solid #28a745;
}

.verb-row .verb {
    font-weight: bold;
    color: #2c3e50;
    background: #e8f5e8;
    padding: 4px 8px;
    border-radius: 4px;
    text-align: center;
}

.verb-row .meaning {
    color: #6c757d;
    font-size: 14px;
}

.verb-row .example {
    color: #495057;
    font-style: italic;
}

/* 둘 다 가능한 동사 테이블 */
.both-table {
    display: flex;
    flex-direction: column;
    gap: 15px;
    margin: 15px 0;
}

.both-row {
    display: grid;
    grid-template-columns: 80px 80px 1fr 1fr;
    gap: 10px;
    align-items: center;
    padding: 15px;
    background: #fff3cd;
    border-radius: 8px;
    border-left: 3px solid #ffc107;
}

.both-row .verb {
    font-weight: bold;
    color: #2c3e50;
    background: #fff;
    padding: 4px 8px;
    border-radius: 4px;
    text-align: center;
}

.both-row .both {
    color: #6c757d;
    font-size: 14px;
}

.both-row .ex1, .both-row .ex2 {
    color: #495057;
    font-size: 13px;
    padding: 8px;
    background: rgba(255,255,255,0.7);
    border-radius: 4px;
}

/* 기억 팁 스타일 */
.memory-tip {
    background: linear-gradient(135deg, #e3f2fd 0%, #bbdefb 100%);
    padding: 15px;
    border-radius: 8px;
    margin-top: 15px;
    border-left: 4px solid #2196f3;
}

.memory-tip strong {
    color: #1976d2;
}

/* 하이라이트 스타일 */
.highlight {
    background: linear-gradient(135deg, #fff3e0 0%, #ffe0b2 100%);
    color: #e65100;
    padding: 2px 6px;
    border-radius: 4px;
    font-weight: bold;
}

/* 퀴즈 컨테이너 스타일 */
.quiz-container {
    background: white;
    padding: 25px;
    border-radius: 15px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.quiz-container h4 {
    color: #2c3e50;
    margin-bottom: 20px;
    font-size: 20px;
    text-align: center;
    padding: 15px;
    background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);
    border-radius: 10px;
}

/* 퀴즈 질문 스타일 */
.question {
    background: #fdfdfd;
    padding: 20px;
    margin: 15px 0;
    border-radius: 12px;
    border: 1px solid #e9ecef;
    box-shadow: 0 2px 6px rgba(0,0,0,0.05);
}

.question p {
    margin-bottom: 15px;
    color: #2c3e50;
    font-weight: 500;
    font-size: 16px;
}

/* 옵션 스타일 */
.options {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.options label {
    display: flex;
    align-items: center;
    padding: 12px 15px;
    background: #f8f9fa;
    border: 2px solid #e9ecef;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
}

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

.options input[type="radio"] {
    margin-right: 12px;
    width: 18px;
    height: 18px;
    accent-color: #2196f3;
}

/* 텍스트 입력 스타일 */
.question input[type="text"] {
    width: 100%;
    padding: 12px 15px;
    border: 2px solid #e9ecef;
    border-radius: 8px;
    font-size: 16px;
    margin-top: 10px;
    transition: border-color 0.3s ease;
}

.question input[type="text"]:focus {
    outline: none;
    border-color: #2196f3;
    box-shadow: 0 0 0 3px rgba(33, 150, 243, 0.1);
}

/* 정답 확인 버튼 개선 */
.check-btn {
    background: linear-gradient(135deg, #28a745 0%, #20c997 100%);
    color: white;
    padding: 15px 30px;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    font-size: 16px;
    font-weight: 600;
    transition: all 0.3s ease;
    box-shadow: 0 6px 20px rgba(40, 167, 69, 0.3);
    position: relative;
    overflow: hidden;
    margin-top: 20px;
    width: 100%;
}

.check-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

.check-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(40, 167, 69, 0.4);
}

.check-btn:hover::before {
    left: 100%;
}

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

/* 오디오 버튼 스타일 */
.audio-btn {
    background: linear-gradient(135deg, #FF6B35 0%, #F7931E 100%);
    color: white;
    border: none;
    padding: 8px 12px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 14px;
    margin-left: 10px;
    transition: all 0.3s ease;
    box-shadow: 0 3px 10px rgba(255, 107, 53, 0.3);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
}

.audio-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

.audio-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(255, 107, 53, 0.4);
    background: linear-gradient(135deg, #E55A2B 0%, #E8831A 100%);
}

.audio-btn:hover::before {
    left: 100%;
}

.audio-btn:active {
    transform: translateY(0);
    box-shadow: 0 2px 8px rgba(255, 107, 53, 0.3);
}

.audio-btn i {
    font-size: 12px;
}

/* 퀴즈 컨트롤 버튼 스타일 */
.quiz-controls {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 20px;
    gap: 15px;
}

.btn {
    padding: 12px 24px;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    font-size: 16px;
    font-weight: 600;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
    min-width: 100px;
}

.btn.primary {
    background: linear-gradient(135deg, #FF6B35 0%, #F7931E 100%);
    color: white;
    box-shadow: 0 6px 20px rgba(255, 107, 53, 0.3);
}

.btn.primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(255, 107, 53, 0.4);
}

.btn.secondary {
    background: linear-gradient(135deg, #6c757d 0%, #495057 100%);
    color: white;
    box-shadow: 0 6px 20px rgba(108, 117, 125, 0.3);
}

.btn.secondary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(108, 117, 125, 0.4);
}

.btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

.btn:hover::before {
    left: 100%;
}

/* 반응형 추가 */
@media (max-width: 768px) {
    .learning-container {
        padding: 20px;
        padding-bottom: 150px; /* 모바일에서 더 많은 하단 여백 */
    }
    
    /* 모바일 레이아웃 통일 */
    .back-header,
    .topic-toggle-container,
    .split-layout {
        max-width: 100%;
        margin-left: 0;
        margin-right: 0;
        padding-left: 20px;
        padding-right: 20px;
        box-sizing: border-box;
    }
    
    .split-layout {
        grid-template-columns: 1fr;
        gap: 20px;
        padding-left: 0;
        padding-right: 0;
    }
    
    .theory-panel,
    .practice-panel {
        margin-left: 0;
        margin-right: 0;
        padding: 20px;
    }
    
    .theory-panel {
        position: static;
        order: 1;
    }
    
    .practice-panel {
        order: 2;
        padding-bottom: 120px; /* 모바일에서 충분한 하단 패딩 */
    }
    
    .back-header {
        padding: 15px 20px;
        flex-direction: row;
        gap: 15px;
        text-align: center;
        align-items: center;
        justify-content: space-between;
    }
    
    .back-header h1 {
        font-size: 20px;
        flex: 1;
        text-align: center;
        margin: 0 10px;
    }
    
    .level-indicator {
        align-self: center;
        font-size: 12px;
        padding: 6px 12px;
    }
    
    .back-button {
        width: 40px;
        height: 40px;
        flex-shrink: 0;
    }
    
    .back-button i {
        font-size: 16px;
    }
    
    .topic-grid {
        grid-template-columns: 1fr;
    }
    
    .tense-timeline {
        flex-direction: column;
        gap: 10px;
    }
    
    .word-order-container {
        justify-content: center;
    }
    
    .reference-grid {
        grid-template-columns: 1fr;
    }
    
    .question-card {
        padding: 20px;
    }
    
    .option-label:hover {
        transform: none;
    }
}

/* 팁 버튼 스타일 */
.tip-btn {
    background: linear-gradient(135deg, #FFD700, #FFA500);
    border: none;
    border-radius: 50%;
    width: 32px;
    height: 32px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    margin-left: 10px;
    transition: all 0.3s ease;
    box-shadow: 0 2px 8px rgba(255, 215, 0, 0.3);
    position: relative;
    z-index: 10;
}

.tip-btn:hover {
    transform: scale(1.1);
    box-shadow: 0 4px 12px rgba(255, 215, 0, 0.4);
}

.tip-btn i {
    color: #fff;
    font-size: 14px;
}

/* 팁 모달 스타일 */
.tip-modal {
    display: none;
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(5px);
    opacity: 0;
    transition: opacity 0.3s ease;
}

.tip-modal.visible {
    opacity: 1;
}

.tip-modal-content {
    background: white;
    margin: 5% auto;
    padding: 0;
    border-radius: 15px;
    width: 90%;
    max-width: 600px;
    max-height: 80vh;
    overflow-y: auto;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
    transform: translateY(-20px);
    transition: transform 0.3s ease;
}

.tip-modal.visible .tip-modal-content {
    transform: translateY(0);
}

.tip-modal-header {
    background: linear-gradient(135deg, #FFD700, #FFA500);
    color: white;
    padding: 20px 25px;
    border-radius: 15px 15px 0 0;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 10;
}

.tip-modal-header h3 {
    margin: 0;
    font-size: 20px;
    font-weight: 600;
}

.tip-close-btn {
    background: rgba(255, 255, 255, 0.2);
    border: none;
    border-radius: 50%;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.3s ease;
    color: white;
}

.tip-close-btn:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: scale(1.1);
}

.tip-modal-body {
    padding: 25px;
    line-height: 1.6;
}

.tip-modal-body h4 {
    color: #333;
    margin: 20px 0 10px 0;
    font-size: 18px;
    font-weight: 600;
}

.tip-modal-body h5 {
    color: #555;
    margin: 15px 0 8px 0;
    font-size: 16px;
    font-weight: 600;
}

.tip-modal-body p {
    color: #666;
    margin: 10px 0;
}

.tip-modal-body ul {
    margin: 10px 0;
    padding-left: 20px;
}

.tip-modal-body li {
    color: #666;
    margin: 8px 0;
    position: relative;
}

/* 스피커 아이콘 스타일 */
.speaker-icon {
    color: #4CAF50;
    cursor: pointer;
    margin-right: 8px;
    transition: all 0.3s ease;
    font-size: 14px;
}

.speaker-icon:hover {
    color: #45a049;
    transform: scale(1.2);
}

/* 반응형 디자인 */
@media (max-width: 768px) {
    .tip-modal-content {
        width: 95%;
        margin: 10% auto;
        max-height: 85vh;
    }
    
    .tip-modal-header {
        padding: 15px 20px;
    }
    
    .tip-modal-header h3 {
        font-size: 18px;
    }
    
    .tip-modal-body {
        padding: 20px;
    }
    
    .tip-btn {
        width: 28px;
        height: 28px;
    }
    
    .tip-btn i {
        font-size: 12px;
    }
}