/* ===== CSS Variables ===== */
:root {
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-tertiary: #f0f2f4;
    --bg-hover: #e8eaed;
    
    --text-primary: #1a1a1a;
    --text-secondary: #4a4a4a;
    --text-muted: #7a7a7a;
    
    --accent-primary: #1a5f3c;
    --accent-secondary: #2d7a50;
    --accent-warning: #b8860b;
    --accent-danger: #c41e3a;
    --accent-purple: #1a5f3c;
    --accent-gradient: linear-gradient(135deg, #1a5f3c 0%, #2d7a50 100%);
    --accent-green-gradient: linear-gradient(135deg, #1a5f3c 0%, #3d9970 100%);
    
    --border-color: #d0d5db;
    --border-radius: 8px;
    --border-radius-lg: 12px;
    
    --font-sans: 'Noto Sans KR', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
    
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.12);
    --shadow-lg: 0 8px 24px rgba(0,0,0,0.16);
    
    --transition: all 0.2s ease;
}

/* ===== Reset & Base ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html, body {
    height: 100%;
}

body {
    font-family: var(--font-sans);
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
}

/* ===== App Layout ===== */
.app-container {
    display: flex;
    height: 100vh;
    overflow: hidden;
}

/* ===== Sidebar ===== */
.sidebar {
    width: 320px;
    min-width: 320px;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    padding: 20px;
}

.logo {
    display: flex;
    align-items: flex-end;
    gap: 12px;
    margin-bottom: 20px;
    text-decoration: none;
}

a.logo {
    margin-bottom: 0;
}

.logo-icon {
    height: 3.36rem;
    width: auto;
    object-fit: contain;
    animation: pulse 8s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; transform: scale(1); }
    50% { opacity: 0.8; transform: scale(1.05); }
}

.logo h1 {
    font-size: 1.1rem;
    font-weight: 600;
    line-height: 1.3;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.logo h1 span {
    font-weight: 400;
    font-size: 0.9rem;
}

.logo-text {
    display: flex;
    flex-direction: column;
}

.logo-subtitle {
    display: block;
    font-size: 0.75rem;
    font-weight: 400;
    color: var(--text-secondary);
    margin-bottom: 2px;
    line-height: 1.15;
}

/* ===== Tab Navigation ===== */
.tab-navigation {
    display: flex;
    gap: 8px;
    margin-bottom: 20px;
    background: var(--bg-tertiary);
    padding: 4px;
    border-radius: var(--border-radius);
}

.tab-btn {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    padding: 10px 12px;
    background: transparent;
    border: none;
    border-radius: 6px;
    color: var(--text-secondary);
    font-size: 0.85rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.tab-btn:hover {
    color: var(--text-primary);
    background: rgba(0, 0, 0, 0.05);
}

.tab-btn.active {
    background: var(--accent-gradient);
    color: white;
    box-shadow: var(--shadow-sm);
}

.tab-btn .tab-icon {
    font-size: 1rem;
}

/* ===== Sidebar Content ===== */
.sidebar-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

/* ===== Search Box ===== */
.search-box {
    position: relative;
    margin-bottom: 12px;
}

.search-box input {
    width: 100%;
    padding: 12px 16px 12px 40px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    color: var(--text-primary);
    font-size: 0.9rem;
    transition: var(--transition);
}

.search-box input:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(26, 95, 60, 0.15);
}

.search-box input::placeholder {
    color: var(--text-muted);
}

.search-icon {
    position: absolute;
    left: 14px;
    top: 50%;
    transform: translateY(-50%);
    opacity: 0.5;
}

/* ===== Sort Info ===== */
.sort-info {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 12px;
    padding: 0 4px;
}

.sort-badge {
    font-size: 0.75rem;
    color: var(--accent-primary);
    background: rgba(26, 95, 60, 0.1);
    padding: 4px 8px;
    border-radius: 4px;
}

.sort-buttons {
    display: flex;
    gap: 6px;
    background: var(--bg-tertiary);
    padding: 4px;
    border-radius: var(--border-radius);
}

.sort-btn {
    display: flex;
    align-items: center;
    gap: 4px;
    padding: 6px 12px;
    background: transparent;
    border: none;
    border-radius: 6px;
    color: var(--text-secondary);
    font-size: 0.8rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.sort-btn:hover {
    color: var(--text-primary);
    background: rgba(0, 0, 0, 0.05);
}

.sort-btn.active {
    background: var(--accent-gradient);
    color: white;
    box-shadow: var(--shadow-sm);
}

.count-badge {
    font-size: 0.75rem;
    color: var(--text-muted);
}

/* ===== Usage Group Header ===== */
.usage-group-header {
    grid-column: 1 / -1;
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    margin-top: 8px;
}

.usage-group-header:first-child {
    margin-top: 0;
}

.usage-group-badge {
    display: inline-flex;
    align-items: center;
    padding: 6px 14px;
    background: var(--accent-gradient);
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
    color: white;
}

.usage-group-badge.no-usage {
    background: linear-gradient(135deg, var(--text-muted) 0%, #6a6a6a 100%);
}

.usage-group-count {
    font-size: 0.8rem;
    color: var(--text-muted);
    font-family: var(--font-mono);
}

/* Usage group header color variations */
.usage-group-header[data-usage="디버깅"] .usage-group-badge {
    background: linear-gradient(135deg, #c41e3a 0%, #dc5064 100%);
}

.usage-group-header[data-usage="최적화"] .usage-group-badge {
    background: linear-gradient(135deg, #b8860b 0%, #d4a532 100%);
}

.usage-group-header[data-usage="설계"] .usage-group-badge {
    background: linear-gradient(135deg, #4682b4 0%, #6496c8 100%);
}

.usage-group-header[data-usage="테스트"] .usage-group-badge {
    background: linear-gradient(135deg, #9370db 0%, #aa8ce6 100%);
}

.usage-group-header[data-usage="문서화"] .usage-group-badge {
    background: linear-gradient(135deg, #3cb371 0%, #5ac88c 100%);
}

.usage-group-header[data-usage="리팩토링"] .usage-group-badge {
    background: linear-gradient(135deg, #ff8c00 0%, #ffaa32 100%);
}

.usage-group-header[data-usage="분석"] .usage-group-badge {
    background: linear-gradient(135deg, #008b8b 0%, #1eaaaa 100%);
}

.usage-group-header[data-usage="자동화"] .usage-group-badge {
    background: linear-gradient(135deg, #6a5acd 0%, #8278dc 100%);
}

.usage-group-header[data-usage="학습"] .usage-group-badge {
    background: linear-gradient(135deg, #ff6347 0%, #ff8264 100%);
}

/* ===== Add Concept Button ===== */
.add-concept-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px;
    background: var(--accent-gradient);
    border-radius: var(--border-radius);
    color: white;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    margin-bottom: 16px;
}

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

.add-concept-btn span {
    font-size: 1.2rem;
    font-weight: 600;
}

/* ===== Concept List ===== */
.concept-list {
    flex: 1;
    overflow-y: auto;
    padding-right: 8px;
}

.concept-list::-webkit-scrollbar {
    width: 6px;
}

.concept-list::-webkit-scrollbar-track {
    background: transparent;
}

.concept-list::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 3px;
}

.concept-item {
    padding: 14px 16px;
    background: var(--bg-tertiary);
    border-radius: var(--border-radius);
    margin-bottom: 8px;
    cursor: pointer;
    transition: var(--transition);
    border: 1px solid transparent;
}

.concept-item:hover {
    background: var(--bg-hover);
    border-color: var(--border-color);
}

.concept-item.active {
    background: rgba(26, 95, 60, 0.08);
    border-color: var(--accent-primary);
}

.concept-item h3 {
    font-size: 0.95rem;
    font-weight: 500;
    margin-bottom: 4px;
    color: var(--text-primary);
    font-family: var(--font-mono);
}

.concept-item .date {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.concept-item .preview {
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-top: 6px;
    line-height: 1.4;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

/* ===== Loading Indicator ===== */
.loading-indicator {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 40px 20px;
    color: var(--text-secondary);
}

.spinner {
    width: 32px;
    height: 32px;
    border: 3px solid var(--border-color);
    border-top-color: var(--accent-primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
    margin-bottom: 12px;
}

.spinner.small {
    width: 16px;
    height: 16px;
    border-width: 2px;
    margin: 0;
    margin-right: 8px;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* ===== Sidebar Footer ===== */
.sidebar-footer {
    padding-top: 16px;
    border-top: 1px solid var(--border-color);
    font-size: 0.75rem;
    color: var(--text-muted);
    text-align: center;
}

/* ===== Main Content ===== */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    background: var(--bg-primary);
}

/* ===== Page Container ===== */
.page-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

/* ===== Empty State ===== */
.empty-state {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 40px;
    text-align: center;
}

.empty-icon {
    font-size: 4rem;
    margin-bottom: 24px;
    animation: float 3s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-10px); }
}

.empty-state h2 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 12px;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.empty-state p {
    color: var(--text-secondary);
    margin-bottom: 32px;
    line-height: 1.8;
}

/* ===== Concept Detail ===== */
.concept-detail {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.concept-detail.read-only .detail-header {
    background: linear-gradient(135deg, rgba(26, 95, 60, 0.08) 0%, rgba(45, 122, 80, 0.06) 100%);
}

.detail-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 24px 32px;
    border-bottom: 1px solid var(--border-color);
    background: var(--bg-secondary);
}

.concept-title-section {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.concept-title-input {
    font-size: 1.8rem;
    font-weight: 700;
    background: transparent;
    border: none;
    color: var(--text-primary);
    font-family: var(--font-mono);
    padding: 0;
}

.concept-title-input:focus {
    outline: none;
    border-bottom: 2px solid var(--accent-primary);
}

.concept-title-display {
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--text-primary);
    font-family: var(--font-mono);
}

.edit-indicator {
    font-size: 0.75rem;
    color: var(--text-muted);
    opacity: 0;
    transition: var(--transition);
}

.concept-title-section:hover .edit-indicator {
    opacity: 1;
}

.concept-usage-section {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-top: 12px;
    padding: 12px 16px;
    background: rgba(26, 95, 60, 0.08);
    border-radius: 8px;
    border: 1px solid rgba(26, 95, 60, 0.15);
}

.usage-label {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-secondary);
    white-space: nowrap;
}

.concept-usage-input {
    flex: 1;
    font-size: 0.95rem;
    font-weight: 500;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 8px 12px;
    border-radius: 6px;
    transition: var(--transition);
}

.concept-usage-input:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 2px rgba(26, 95, 60, 0.15);
}

.concept-usage-input::placeholder {
    color: var(--text-muted);
}

.read-only-badge {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    font-size: 0.8rem;
    color: var(--accent-secondary);
    background: rgba(26, 95, 60, 0.12);
    padding: 4px 10px;
    border-radius: 20px;
    margin-top: 4px;
}

.header-actions {
    display: flex;
    gap: 8px;
}

.icon-btn {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    cursor: pointer;
    font-size: 1.1rem;
    transition: var(--transition);
}

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

.delete-btn:hover {
    background: rgba(196, 30, 58, 0.15);
    border-color: var(--accent-danger);
}

.regenerate-btn:hover {
    background: rgba(26, 95, 60, 0.15);
    border-color: var(--accent-primary);
}

/* ===== Content Area ===== */
.content-area {
    flex: 1;
    overflow-y: auto;
    padding: 32px;
}

.markdown-content {
    max-width: 800px;
    font-size: 1rem;
    line-height: 1.8;
}

.markdown-content h2 {
    font-size: 1.3rem;
    font-weight: 600;
    margin: 32px 0 16px;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--border-color);
    color: var(--accent-primary);
}

.markdown-content h2:first-child {
    margin-top: 0;
}

.markdown-content p {
    margin-bottom: 16px;
    color: var(--text-secondary);
}

.markdown-content ul, .markdown-content ol {
    margin: 16px 0;
    padding-left: 24px;
}

.markdown-content li {
    margin-bottom: 12px;
    color: var(--text-secondary);
    line-height: 1.7;
}

.markdown-content code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    padding: 2px 8px;
    background: var(--bg-tertiary);
    border-radius: 4px;
    color: var(--accent-purple);
}

.markdown-content pre {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 16px;
    overflow-x: auto;
    margin: 16px 0;
}

.markdown-content pre code {
    padding: 0;
    background: none;
    color: var(--text-primary);
}

.markdown-content blockquote {
    border-left: 3px solid var(--accent-primary);
    padding-left: 16px;
    margin: 16px 0;
    color: var(--text-secondary);
    font-style: italic;
}

/* 한 줄 요약 스타일 (💡 아이콘이 포함된 blockquote) */
.markdown-content blockquote:first-of-type {
    background: linear-gradient(135deg, rgba(26, 95, 60, 0.08) 0%, rgba(45, 122, 80, 0.06) 100%);
    border-left: 4px solid var(--accent-purple);
    border-radius: 0 var(--border-radius) var(--border-radius) 0;
    padding: 16px 20px;
    margin: 0 0 24px 0;
    font-size: 1.1rem;
    font-style: normal;
    font-weight: 500;
    color: var(--text-primary);
    line-height: 1.6;
}

.markdown-content strong {
    color: var(--text-primary);
    font-weight: 600;
}

/* ===== Definition Card ===== */
.definition-card {
    background: linear-gradient(135deg, #f8faf9 0%, #f0f5f2 100%);
    border: 2px solid var(--accent-primary);
    border-radius: var(--border-radius-lg);
    margin: 24px 0;
    overflow: hidden;
    box-shadow: 0 4px 16px rgba(26, 95, 60, 0.1);
}

.definition-header {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 16px 20px;
    background: linear-gradient(135deg, var(--accent-primary) 0%, var(--accent-secondary) 100%);
}

.definition-header .definition-icon {
    font-size: 1.3rem;
}

.definition-header h2 {
    font-size: 1.1rem;
    font-weight: 600;
    color: white;
    margin: 0;
    padding: 0;
    border: none;
}

.definition-content {
    padding: 20px 24px;
    background: white;
}

.definition-content p {
    color: var(--text-primary);
    font-size: 1rem;
    line-height: 1.8;
    margin: 0;
}

.definition-content ul,
.definition-content ol {
    margin: 12px 0;
    padding-left: 20px;
}

.definition-content li {
    color: var(--text-primary);
    margin-bottom: 8px;
}

/* ===== Edit Textarea ===== */
.edit-textarea {
    width: 100%;
    height: 100%;
    min-height: 400px;
    padding: 24px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 0.9rem;
    line-height: 1.6;
    resize: none;
}

.edit-textarea:focus {
    outline: none;
    border-color: var(--accent-primary);
}

/* ===== Detail Footer ===== */
.detail-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 32px;
    border-top: 1px solid var(--border-color);
    background: var(--bg-secondary);
}

.meta-info {
    font-size: 0.8rem;
    color: var(--text-muted);
}

.footer-actions {
    display: flex;
    gap: 12px;
}

/* ===== Buttons ===== */
.primary-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 24px;
    background: var(--accent-gradient);
    border: none;
    border-radius: var(--border-radius);
    color: white;
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

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

.primary-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.secondary-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 12px 24px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    color: var(--text-primary);
    font-size: 0.95rem;
    cursor: pointer;
    transition: var(--transition);
}

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

/* ===== Modal ===== */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.7);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    backdrop-filter: blur(4px);
}

.modal {
    width: 90%;
    max-width: 500px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-lg);
    animation: modalIn 0.2s ease;
}

@keyframes modalIn {
    from {
        opacity: 0;
        transform: scale(0.95) translateY(-20px);
    }
    to {
        opacity: 1;
        transform: scale(1) translateY(0);
    }
}

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 20px 24px;
    border-bottom: 1px solid var(--border-color);
}

.modal-header h2 {
    font-size: 1.2rem;
    font-weight: 600;
}

.close-btn {
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: transparent;
    border: none;
    color: var(--text-secondary);
    font-size: 1.5rem;
    cursor: pointer;
    border-radius: 50%;
    transition: var(--transition);
}

.close-btn:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.modal-body {
    padding: 24px;
}

.modal-body label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    color: var(--text-primary);
}

.modal-body input {
    width: 100%;
    padding: 14px 16px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    color: var(--text-primary);
    font-size: 1rem;
    transition: var(--transition);
}

.modal-body input:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(26, 95, 60, 0.15);
}

.helper-text {
    margin-top: 12px;
    font-size: 0.85rem;
    color: var(--text-muted);
}

/* ===== Example Prompts Cards ===== */
.example-prompts-section {
    margin-top: 20px;
}

.example-label {
    display: block;
    margin-bottom: 12px;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-primary);
}

.example-cards {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 10px;
}

.example-card {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 14px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transition);
}

.example-card:hover {
    background: var(--bg-hover);
    border-color: var(--accent-primary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
}

.example-card:active {
    transform: translateY(0);
}

.example-card.selected {
    background: rgba(26, 95, 60, 0.12);
    border-color: var(--accent-primary);
}

.example-icon {
    font-size: 1.2rem;
    line-height: 1;
}

.example-text {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--text-primary);
    font-weight: 500;
    flex: 1;
}

.example-usage {
    font-size: 0.65rem;
    font-weight: 600;
    padding: 2px 6px;
    background: rgba(26, 95, 60, 0.12);
    color: var(--accent-primary);
    border-radius: 10px;
    white-space: nowrap;
}

.modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: 12px;
    padding: 20px 24px;
    border-top: 1px solid var(--border-color);
}

/* ===== Toast ===== */
.toast {
    position: fixed;
    bottom: 24px;
    right: 24px;
    padding: 16px 24px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    color: var(--text-primary);
    font-size: 0.9rem;
    z-index: 2000;
    transform: translateY(100px);
    opacity: 0;
    transition: all 0.3s ease;
}

.toast.show {
    transform: translateY(0);
    opacity: 1;
}

.toast.success {
    border-left: 4px solid var(--accent-secondary);
}

.toast.error {
    border-left: 4px solid var(--accent-danger);
}

.toast.info {
    border-left: 4px solid var(--accent-primary);
}

/* ===== Highlight Search Match ===== */
.highlight {
    background: rgba(26, 95, 60, 0.2);
    color: var(--text-primary);
    padding: 0 2px;
    border-radius: 2px;
}

/* ===== App Header ===== */
.app-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 6px 24px;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
}

.header-left {
    display: flex;
    align-items: center;
    gap: 20px;
}

.app-slogan {
    font-size: 0.9rem;
    font-style: italic;
    color: var(--accent-primary);
    font-weight: 500;
    padding-left: 16px;
    border-left: 2px solid var(--accent-primary);
    line-height: 1.4;
    letter-spacing: 0.02em;
}

.header-right {
    display: flex;
    align-items: center;
}

/* ===== Header Slogan ===== */
.header-slogan {
    flex: 1;
    display: flex;
    justify-content: center;
    padding: 0 20px;
}

.slogan-text {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-secondary);
    letter-spacing: 0.02em;
    white-space: nowrap;
}

/* ===== Header Nav Group ===== */
.header-nav-group {
    display: flex;
    align-items: center;
    gap: 16px;
}

/* ===== User Menu ===== */
.user-menu,
.admin-menu {
    display: flex;
    align-items: center;
    gap: 12px;
}

.user-email {
    font-size: 0.85rem;
    color: var(--text-secondary);
    padding: 6px 12px;
    background: var(--bg-tertiary);
    border-radius: 20px;
    max-width: 180px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.admin-badge {
    font-size: 0.85rem;
    color: #c41e3a;
    padding: 6px 12px;
    background: rgba(196, 30, 58, 0.1);
    border: 1px solid rgba(196, 30, 58, 0.3);
    border-radius: 20px;
    font-weight: 600;
}

.logout-btn {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 8px 14px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    color: var(--text-secondary);
    font-size: 0.85rem;
    cursor: pointer;
    transition: var(--transition);
}

.logout-btn:hover {
    background: rgba(196, 30, 58, 0.1);
    border-color: #c41e3a;
    color: #c41e3a;
}

.logout-btn.admin {
    background: rgba(196, 30, 58, 0.1);
    border-color: rgba(196, 30, 58, 0.3);
    color: #c41e3a;
}

.logout-btn.admin:hover {
    background: rgba(196, 30, 58, 0.2);
}

.powered-by {
    font-size: 0.75rem;
    color: var(--text-muted);
}

/* ===== Page Navigation (Tab Style) ===== */
.page-navigation {
    display: flex;
    gap: 0;
    background: transparent;
    padding: 0;
    border-radius: 0;
}

.page-nav-btn,
.page-nav-link {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    background: transparent;
    border: none;
    border-bottom: 2px solid transparent;
    border-radius: 0;
    color: var(--text-muted);
    font-size: 0.85rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
    position: relative;
}

.page-nav-btn:hover,
.page-nav-link:hover {
    color: var(--text-primary);
    background: transparent;
    border-bottom-color: var(--border-color);
}

.page-nav-btn.active,
.page-nav-link.active {
    background: transparent;
    color: var(--accent-primary);
    border-bottom-color: var(--accent-primary);
    font-weight: 600;
    box-shadow: none;
}

.nav-icon {
    font-size: 1rem;
}

.nav-text {
    font-size: 0.85rem;
}

/* ===== Page Content ===== */
.page-content {
    padding: 24px;
    min-height: calc(100vh - 60px);
}

/* ===== List View ===== */
.list-view {
    max-width: 1200px;
    margin: 0 auto;
}

.list-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 24px;
}

.list-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-primary);
}

.list-actions {
    display: flex;
    align-items: center;
    gap: 12px;
}

.list-info {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 16px;
}

.add-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 10px 16px;
    background: var(--accent-gradient);
    border: none;
    border-radius: var(--border-radius);
    color: white;
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

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

/* ===== Concept Grid ===== */
.concept-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 16px;
}

.concept-card-item {
    padding: 20px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    cursor: pointer;
    transition: var(--transition);
}

.concept-card-item:hover {
    background: var(--bg-tertiary);
    border-color: var(--accent-primary);
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

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

.concept-card-item h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin: 0;
    color: var(--text-primary);
    font-family: var(--font-mono);
    flex: 1;
    min-width: 0;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

/* ===== Usage Badge ===== */
.usage-badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 4px 10px;
    background: linear-gradient(135deg, rgba(26, 95, 60, 0.15) 0%, rgba(45, 122, 80, 0.1) 100%);
    border: 1px solid var(--accent-primary);
    border-radius: 20px;
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--accent-primary);
    white-space: nowrap;
    flex-shrink: 0;
    transition: var(--transition);
}

.usage-badge:hover {
    transform: scale(1.05);
    box-shadow: 0 2px 8px rgba(26, 95, 60, 0.2);
}

/* Usage badge color variations based on content (applied via JS data attribute) */
.usage-badge[data-usage="디버깅"] {
    background: linear-gradient(135deg, rgba(196, 30, 58, 0.15) 0%, rgba(220, 80, 100, 0.1) 100%);
    border-color: #c41e3a;
    color: #c41e3a;
}

.usage-badge[data-usage="최적화"] {
    background: linear-gradient(135deg, rgba(184, 134, 11, 0.15) 0%, rgba(200, 160, 50, 0.1) 100%);
    border-color: #b8860b;
    color: #b8860b;
}

.usage-badge[data-usage="설계"] {
    background: linear-gradient(135deg, rgba(70, 130, 180, 0.15) 0%, rgba(100, 150, 200, 0.1) 100%);
    border-color: #4682b4;
    color: #4682b4;
}

.usage-badge[data-usage="테스트"] {
    background: linear-gradient(135deg, rgba(147, 112, 219, 0.15) 0%, rgba(170, 140, 230, 0.1) 100%);
    border-color: #9370db;
    color: #9370db;
}

.usage-badge[data-usage="문서화"] {
    background: linear-gradient(135deg, rgba(60, 179, 113, 0.15) 0%, rgba(90, 200, 140, 0.1) 100%);
    border-color: #3cb371;
    color: #3cb371;
}

.usage-badge[data-usage="리팩토링"] {
    background: linear-gradient(135deg, rgba(255, 140, 0, 0.15) 0%, rgba(255, 170, 50, 0.1) 100%);
    border-color: #ff8c00;
    color: #ff8c00;
}

.usage-badge[data-usage="분석"] {
    background: linear-gradient(135deg, rgba(0, 139, 139, 0.15) 0%, rgba(30, 170, 170, 0.1) 100%);
    border-color: #008b8b;
    color: #008b8b;
}

.usage-badge[data-usage="자동화"] {
    background: linear-gradient(135deg, rgba(106, 90, 205, 0.15) 0%, rgba(130, 120, 220, 0.1) 100%);
    border-color: #6a5acd;
    color: #6a5acd;
}

.usage-badge[data-usage="학습"] {
    background: linear-gradient(135deg, rgba(255, 99, 71, 0.15) 0%, rgba(255, 130, 100, 0.1) 100%);
    border-color: #ff6347;
    color: #ff6347;
}

.concept-card-item .preview {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.5;
    margin-bottom: 12px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.concept-card-item .date {
    font-size: 0.75rem;
    color: var(--text-muted);
}

/* ===== Detail View ===== */
.detail-view {
    max-width: 900px;
    margin: 0 auto;
}

.detail-nav {
    margin-bottom: 20px;
}

.back-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    color: var(--text-secondary);
    font-size: 0.9rem;
    cursor: pointer;
    transition: var(--transition);
}

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

/* ===== Concept Card (Detail) ===== */
.concept-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    overflow: hidden;
}

.concept-card.read-only {
    border-color: var(--accent-secondary);
}

.concept-card .card-header {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    padding: 24px;
    border-bottom: 1px solid var(--border-color);
    background: var(--bg-tertiary);
}

.concept-card .card-content {
    padding: 24px;
    min-height: 300px;
}

.concept-card .card-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 24px;
    border-top: 1px solid var(--border-color);
    background: var(--bg-tertiary);
}

/* ===== Quiz Page Styles ===== */

/* Quiz Start View */
.quiz-start-view {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: calc(100vh - 120px);
}

.quiz-start-container {
    max-width: 600px;
    text-align: center;
    padding: 40px;
}

.quiz-hero {
    margin-bottom: 32px;
}

.quiz-hero-icon {
    font-size: 4rem;
    margin-bottom: 16px;
    animation: bounce 2s ease-in-out infinite;
}

@keyframes bounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-10px); }
}

.quiz-hero h1 {
    font-size: 2.2rem;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 12px;
}

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

.quiz-stats-cards {
    display: flex;
    gap: 16px;
    justify-content: center;
    margin-bottom: 32px;
}

.stat-card {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 16px 20px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    min-width: 140px;
}

.stat-icon {
    font-size: 1.5rem;
}

.stat-info {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
}

.stat-value {
    font-size: 1.3rem;
    font-weight: 700;
    color: var(--accent-primary);
    font-family: var(--font-mono);
}

.stat-label {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.quiz-rules {
    text-align: left;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 24px;
    margin-bottom: 32px;
}

.quiz-rules h3 {
    font-size: 1rem;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.quiz-rules ul {
    list-style: none;
    padding: 0;
}

.quiz-rules li {
    padding: 8px 0;
    padding-left: 24px;
    position: relative;
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.quiz-rules li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--accent-primary);
    font-weight: bold;
}

.start-quiz-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    padding: 16px 48px;
    background: var(--accent-gradient);
    border: none;
    border-radius: var(--border-radius-lg);
    color: white;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: var(--shadow-md);
}

.start-quiz-btn:hover:not(:disabled) {
    transform: translateY(-3px) scale(1.02);
    box-shadow: 0 12px 24px rgba(26, 95, 60, 0.3);
}

.start-quiz-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

.start-quiz-btn .btn-icon {
    font-size: 1.3rem;
}

.quiz-note {
    margin-top: 16px;
    font-size: 0.85rem;
    color: var(--text-muted);
}

/* Quiz Play View */
.quiz-play-view {
    display: flex;
    align-items: flex-start;
    justify-content: center;
    min-height: calc(100vh - 120px);
    padding-top: 20px;
}

.quiz-container {
    max-width: 700px;
    width: 100%;
}

.quiz-progress {
    margin-bottom: 24px;
}

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

.progress-fill {
    height: 100%;
    background: var(--accent-gradient);
    border-radius: 4px;
    transition: width 0.3s ease;
}

.progress-text {
    text-align: center;
    font-size: 0.9rem;
    color: var(--text-secondary);
    font-family: var(--font-mono);
}

.quiz-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 32px;
    margin-bottom: 24px;
}

.quiz-card-header {
    display: flex;
    gap: 12px;
    margin-bottom: 20px;
}

.question-badge {
    padding: 6px 12px;
    background: rgba(26, 95, 60, 0.12);
    color: var(--accent-primary);
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
}

.concept-name-badge {
    padding: 6px 12px;
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    border-radius: 20px;
    font-size: 0.8rem;
    font-family: var(--font-mono);
}

.quiz-question {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 28px;
    line-height: 1.6;
}

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

.quiz-option {
    display: flex;
    align-items: flex-start;
    gap: 14px;
    padding: 16px 20px;
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: all 0.2s ease;
    text-align: left;
}

.quiz-option:hover:not(:disabled) {
    border-color: var(--accent-primary);
    background: rgba(26, 95, 60, 0.05);
    transform: translateX(4px);
}

.quiz-option:disabled {
    cursor: default;
}

.quiz-option.correct {
    border-color: #2d7a50;
    background: rgba(45, 122, 80, 0.15);
}

.quiz-option.incorrect {
    border-color: #c41e3a;
    background: rgba(196, 30, 58, 0.1);
}

.option-letter {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    background: var(--bg-tertiary);
    border-radius: 50%;
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--text-secondary);
    flex-shrink: 0;
}

.quiz-option:hover:not(:disabled) .option-letter {
    background: var(--accent-primary);
    color: white;
}

.quiz-option.correct .option-letter {
    background: #2d7a50;
    color: white;
}

.quiz-option.incorrect .option-letter {
    background: #c41e3a;
    color: white;
}

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

.quiz-result {
    margin-top: 24px;
    padding: 20px;
    background: var(--bg-tertiary);
    border-radius: var(--border-radius);
    animation: slideDown 0.3s ease;
}

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

.result-icon {
    font-size: 2rem;
    text-align: center;
    margin-bottom: 8px;
}

.result-text {
    text-align: center;
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 16px;
}

.result-text.correct {
    color: #2d7a50;
}

.result-text.incorrect {
    color: #c41e3a;
}

.explanation-box {
    background: var(--bg-primary);
    border-left: 3px solid var(--accent-primary);
    padding: 16px;
    border-radius: 0 var(--border-radius) var(--border-radius) 0;
}

.explanation-box h4 {
    font-size: 0.9rem;
    color: var(--accent-primary);
    margin-bottom: 8px;
}

.explanation-box p {
    font-size: 0.95rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

.quiz-actions {
    display: flex;
    justify-content: space-between;
    gap: 16px;
}

.quit-quiz-btn {
    padding: 12px 24px;
    background: transparent;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    color: var(--text-secondary);
    font-size: 0.9rem;
    cursor: pointer;
    transition: var(--transition);
}

.quit-quiz-btn:hover {
    background: rgba(196, 30, 58, 0.1);
    border-color: #c41e3a;
    color: #c41e3a;
}

.next-question-btn {
    padding: 12px 32px;
    background: var(--accent-gradient);
    border: none;
    border-radius: var(--border-radius);
    color: white;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    margin-left: auto;
}

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

/* Quiz Result View */
.quiz-result-view {
    display: flex;
    align-items: flex-start;
    justify-content: center;
    min-height: calc(100vh - 120px);
    padding-top: 20px;
}

.result-container {
    max-width: 700px;
    width: 100%;
}

.result-hero {
    text-align: center;
    margin-bottom: 24px;
}

.result-score-circle {
    width: 140px;
    height: 140px;
    border-radius: 50%;
    background: var(--bg-secondary);
    border: 4px solid var(--border-color);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    margin: 0 auto 20px;
    transition: all 0.3s ease;
}

.result-score-circle.high-score {
    border-color: #2d7a50;
    background: rgba(45, 122, 80, 0.1);
}

.result-score-circle.low-score {
    border-color: #c41e3a;
    background: rgba(196, 30, 58, 0.1);
}

.score-value {
    font-size: 3rem;
    font-weight: 700;
    color: var(--accent-primary);
    font-family: var(--font-mono);
    line-height: 1;
}

.result-score-circle.high-score .score-value {
    color: #2d7a50;
}

.result-score-circle.low-score .score-value {
    color: #c41e3a;
}

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

.result-hero h1 {
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 8px;
}

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

.result-grade {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    padding: 16px 24px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    margin-bottom: 32px;
}

.grade-emoji {
    font-size: 2rem;
}

.grade-text {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--accent-primary);
}

.result-details {
    margin-bottom: 32px;
}

.result-details h3 {
    font-size: 1.1rem;
    color: var(--text-primary);
    margin-bottom: 16px;
}

.result-list {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.result-item {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 20px;
    transition: var(--transition);
}

.result-item.correct {
    border-left: 4px solid #2d7a50;
}

.result-item.incorrect {
    border-left: 4px solid #c41e3a;
}

.result-item-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 12px;
}

.result-item-num {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    background: var(--bg-tertiary);
    border-radius: 50%;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.result-item-icon {
    font-size: 1.2rem;
}

.result-item-concept {
    padding: 4px 10px;
    background: var(--bg-tertiary);
    border-radius: 12px;
    font-size: 0.8rem;
    font-family: var(--font-mono);
    color: var(--text-secondary);
}

.result-item-question {
    font-size: 1rem;
    color: var(--text-primary);
    margin-bottom: 16px;
    line-height: 1.5;
}

.result-item-answers {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-bottom: 12px;
}

.user-answer,
.correct-answer {
    display: flex;
    gap: 8px;
    padding: 10px 14px;
    border-radius: var(--border-radius);
    font-size: 0.9rem;
}

.user-answer.correct {
    background: rgba(45, 122, 80, 0.1);
}

.user-answer.incorrect {
    background: rgba(196, 30, 58, 0.1);
}

.correct-answer {
    background: rgba(45, 122, 80, 0.15);
    border: 1px solid rgba(45, 122, 80, 0.3);
}

.answer-label {
    font-weight: 600;
    color: var(--text-secondary);
    white-space: nowrap;
}

.answer-text {
    color: var(--text-primary);
}

.result-item-explanation {
    background: var(--bg-tertiary);
    padding: 14px;
    border-radius: var(--border-radius);
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

.result-item-explanation strong {
    color: var(--accent-primary);
}

.result-actions {
    display: flex;
    justify-content: center;
    gap: 16px;
}

.retry-quiz-btn {
    padding: 14px 28px;
    background: var(--accent-gradient);
    border: none;
    border-radius: var(--border-radius);
    color: white;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

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

.back-to-start-btn {
    padding: 14px 28px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    color: var(--text-primary);
    font-size: 1rem;
    cursor: pointer;
    transition: var(--transition);
}

.back-to-start-btn:hover {
    background: var(--bg-hover);
}

/* ===== Site Footer ===== */
.site-footer {
    background: var(--accent-gradient);
    color: #ffffff;
    padding: 32px 32px 24px;
    margin-top: auto;
}

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

.footer-top {
    display: flex;
    align-items: center;
    gap: 16px;
    margin-bottom: 20px;
}

.footer-logo-wrapper {
    display: flex;
    align-items: center;
    gap: 14px;
}

.footer-logo {
    height: 52px;
    width: auto;
    object-fit: contain;
}

.footer-brand {
    display: flex;
    flex-direction: column;
    gap: 0;
    line-height: 1.2;
}

.footer-brand-ko {
    font-size: 1.1rem;
    font-weight: 400;
    color: #ffffff;
    letter-spacing: 0.02em;
}

.footer-brand-en {
    font-size: 0.85rem;
    font-weight: 400;
    color: rgba(255, 255, 255, 0.9);
    letter-spacing: 0.01em;
}

.footer-info {
    display: flex;
    flex-direction: column;
    gap: 6px;
    margin-top: 4px;
}

.footer-info-item {
    font-size: 0.85rem;
    color: rgba(255, 255, 255, 0.85);
    line-height: 1.4;
}

.footer-info-item a {
    color: rgba(255, 255, 255, 0.85);
    text-decoration: none;
    transition: color 0.2s ease;
}

.footer-info-item a:hover {
    color: #ffffff;
    text-decoration: underline;
}

.footer-divider {
    height: 1px;
    background: rgba(255, 255, 255, 0.2);
    margin: 16px 0;
}

.footer-copyright {
    font-size: 0.8rem;
    color: rgba(255, 255, 255, 0.7);
    text-align: center;
}

.footer-info {
    text-align: left;
}

.footer-top {
    justify-content: flex-start;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .app-container {
        flex-direction: column;
    }
    
    .sidebar {
        width: 100%;
        min-width: 100%;
        height: auto;
        max-height: 40vh;
    }
    
    .concept-list {
        max-height: 150px;
    }
    
    .detail-header {
        padding: 16px 20px;
    }
    
    .concept-title-input,
    .concept-title-display {
        font-size: 1.4rem;
    }
    
    .content-area {
        padding: 20px;
    }
    
    .detail-footer {
        padding: 12px 20px;
        flex-direction: column;
        gap: 12px;
    }
    
    .tab-btn span:not(.tab-icon) {
        display: none;
    }
    
    .tab-btn .tab-icon {
        font-size: 1.2rem;
    }
    
    /* Quiz responsive */
    .quiz-stats-cards {
        flex-direction: column;
    }
    
    .stat-card {
        min-width: 100%;
    }
    
    .quiz-hero h1 {
        font-size: 1.6rem;
    }
    
    .quiz-card {
        padding: 20px;
    }
    
    .quiz-question {
        font-size: 1.1rem;
    }
    
    .quiz-actions {
        flex-direction: column;
    }
    
    .result-actions {
        flex-direction: column;
    }
    
    .nav-text {
        display: none;
    }
    
    .page-nav-btn {
        padding: 10px 12px;
    }
    
    .app-slogan {
        display: none;
    }
    
    /* Footer responsive */
    .site-footer {
        padding: 24px 16px 20px;
    }
    
    .footer-top {
        flex-direction: column;
        align-items: flex-start;
        gap: 12px;
    }
    
    .footer-logo {
        height: 40px;
    }
    
    .footer-brand-ko {
        font-size: 1rem;
    }
    
    .footer-brand-en {
        font-size: 0.8rem;
    }
    
    .footer-info-item {
        font-size: 0.8rem;
    }
    
    .footer-copyright {
        font-size: 0.75rem;
    }
}