/* CSS 변수를 통한 테마 설정 */
:root {
    --primary-color: #3b82f6;
    --primary-dark: #2563eb;
    --success-color: #10b981;
    --error-color: #ef4444;
    --warning-color: #f59e0b;
    
    /* 라이트 테마 */
    --bg-color: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --modal-bg: rgba(0, 0, 0, 0.5);
}

/* 다크 테마 */
[data-theme="dark"] {
    --bg-color: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --border-color: #475569;
    --shadow-color: rgba(0, 0, 0, 0.3);
    --modal-bg: rgba(0, 0, 0, 0.7);
}

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

body {
    font-family: 'Noto Sans KR', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.hidden {
    display: none !important;
}

/* 모달 스타일 */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--modal-bg);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
    backdrop-filter: blur(5px);
}

.modal-content {
    background: var(--bg-color);
    padding: 3rem;
    border-radius: 20px;
    box-shadow: 0 25px 50px var(--shadow-color);
    max-width: 450px;
    width: 90%;
    animation: modalSlideUp 0.3s ease;
}

@keyframes modalSlideUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.modal-header {
    text-align: center;
    margin-bottom: 2rem;
}

.modal-header h2 {
    color: var(--text-primary);
    font-size: 1.8rem;
    margin-bottom: 0.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.modal-header p {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.input-group {
    margin-bottom: 1.5rem;
}

.input-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
}

.input-group input {
    width: 100%;
    padding: 1rem;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    font-size: 1rem;
    background: var(--bg-secondary);
    color: var(--text-primary);
    transition: border-color 0.3s ease;
}

.input-group input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.auth-btn {
    width: 100%;
    padding: 1rem;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 12px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    transition: background-color 0.3s ease;
}

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

.error-message {
    color: var(--error-color);
    font-size: 0.9rem;
    margin-top: 1rem;
    text-align: center;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.error-message.show {
    opacity: 1;
}

/* 헤더 */
.header {
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(10px);
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.header h1 {
    font-size: 1.8rem;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

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

.theme-toggle, .logout-btn {
    padding: 0.7rem 1.2rem;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: all 0.3s ease;
}

.theme-toggle {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.theme-toggle:hover {
    background: var(--border-color);
}

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

.logout-btn:hover {
    background: #dc2626;
}

/* 메인 콘텐츠 */
.main-content {
    animation: fadeIn 0.5s ease;
}

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

section {
    margin: 3rem 0;
    padding: 2rem;
    background: var(--bg-secondary);
    border-radius: 16px;
    border: 1px solid var(--border-color);
}

section h2 {
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* 커버 이미지 */
.cover-section {
    text-align: center;
}

.cover-placeholder {
    background: var(--bg-tertiary);
    border: 2px dashed var(--border-color);
    padding: 4rem 2rem;
    border-radius: 16px;
    color: var(--text-secondary);
}

.cover-placeholder i {
    font-size: 3rem;
    margin-bottom: 1rem;
}

/* 소개 섹션 */
.intro-section p {
    font-size: 1.1rem;
    color: var(--text-secondary);
    line-height: 1.8;
}

/* 다운로드 섹션 */
.download-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
}

.download-item {
    background: var(--bg-color);
    padding: 1.5rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    text-align: center;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.download-item:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px var(--shadow-color);
}

.download-item i {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.download-item h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.download-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    background: var(--primary-color);
    color: white;
    text-decoration: none;
    padding: 0.7rem 1.5rem;
    border-radius: 10px;
    font-weight: 500;
    transition: background-color 0.3s ease;
}

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

/* 비디오 섹션 */
.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
}

.video-item {
    background: var(--bg-color);
    border-radius: 12px;
    border: 1px solid var(--border-color);
    overflow: hidden;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.video-item:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px var(--shadow-color);
}

.video-header {
    padding: 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
}

.video-header h3 {
    color: var(--text-primary);
    font-size: 1.1rem;
}

.video-controls {
    display: flex;
    gap: 0.5rem;
}

.embed-btn, .external-btn {
    padding: 0.5rem 1rem;
    border: none;
    border-radius: 8px;
    font-size: 0.85rem;
    cursor: pointer;
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 0.3rem;
    transition: all 0.3s ease;
}

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

.embed-btn:hover {
    background: #059669;
}

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

.external-btn:hover {
    background: var(--border-color);
}

.video-embed {
    padding: 1rem;
    min-height: 50px;
}

.video-embed iframe {
    width: 100%;
    height: 250px;
    border: none;
    border-radius: 8px;
}

/* PDF 섹션 */
.pdf-item {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    background: var(--bg-color);
    padding: 2rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.pdf-item:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px var(--shadow-color);
}

.pdf-icon {
    font-size: 3rem;
    color: var(--error-color);
}

.pdf-info h3 {
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.pdf-info p {
    color: var(--text-secondary);
}

/* 문의 섹션 */
.contact-info {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
}

.contact-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem;
    background: var(--bg-color);
    border-radius: 10px;
    border: 1px solid var(--border-color);
}

.contact-item i {
    color: var(--primary-color);
    font-size: 1.2rem;
}

.contact-item a {
    color: var(--text-primary);
    text-decoration: none;
    transition: color 0.3s ease;
}

.contact-item a:hover {
    color: var(--primary-color);
}

/* 푸터 */
.footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: 2rem 0;
    margin-top: 4rem;
    text-align: center;
    color: var(--text-secondary);
}

/* 반응형 디자인 */
@media (max-width: 768px) {
    .container {
        padding: 0 15px;
    }
    
    section {
        padding: 1.5rem;
        margin: 2rem 0;
    }
    
    .header-content {
        flex-direction: column;
        gap: 1rem;
        align-items: center;
    }
    
    .header h1 {
        font-size: 1.5rem;
    }
    
    .video-grid {
        grid-template-columns: 1fr;
    }
    
    .download-grid {
        grid-template-columns: 1fr;
    }
    
    .contact-info {
        grid-template-columns: 1fr;
    }
    
    .modal-content {
        padding: 2rem;
        margin: 1rem;
    }
    
    .pdf-item {
        flex-direction: column;
        text-align: center;
    }
    
    .video-controls {
        flex-direction: column;
        gap: 0.5rem;
    }
    
    .embed-btn, .external-btn {
        width: 100%;
        justify-content: center;
    }
}

@media (max-width: 480px) {
    .header-controls {
        flex-direction: column;
        gap: 0.5rem;
        width: 100%;
    }
    
    .theme-toggle, .logout-btn {
        width: 100%;
        justify-content: center;
    }
    
    .video-header {
        flex-direction: column;
        gap: 1rem;
        align-items: stretch;
    }
    
    .video-controls {
        justify-content: center;
    }
}