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

:root {
    --primary: #1e88e5;
    --primary-dark: #1565c0;
    --secondary: #00bcd4;
    --accent: #ff7043;
    --accent-light: #ffab91;
    --bg-light: #f5f7fa;
    --white: #ffffff;
    --text-dark: #263238;
    --text-light: #546e7a;
    --border: #e0e7ff;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    --shadow-hover: 0 8px 30px rgba(0, 0, 0, 0.12);
    --radius: 12px;
    --radius-sm: 8px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
    background: linear-gradient(135deg, #f5f7fa 0%, #e4edf5 100%);
    color: var(--text-dark);
    line-height: 1.6;
    min-height: 100vh;
    font-size: 16px;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

.navbar {
    background: var(--white);
    padding: 12px 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
}

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

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
}

.logo-icon {
    display: flex;
    align-items: center;
    justify-content: center;
}

.logo-icon svg {
    display: block;
    height: 50px;
    width: auto;
}

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

.logo-title {
    font-size: 1.1rem;
    font-weight: 700;
    color: #00bcd4;
    letter-spacing: 1px;
}

.logo-subtitle {
    font-size: 0.7rem;
    color: #546e7a;
    letter-spacing: 0.5px;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 32px;
}

.nav-links a {
    color: var(--text-dark);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s;
    font-size: 1rem;
}

.nav-links a:hover {
    color: var(--secondary);
}

.hero {
    padding: 80px 0 60px;
    text-align: center;
    background: var(--white);
    border-bottom: 1px solid var(--border);
}

.hero h1 {
    font-size: 2.5rem;
    color: var(--text-dark);
    margin-bottom: 16px;
    font-weight: 700;
}

.hero p {
    font-size: 1.15rem;
    color: var(--text-light);
}

.main-content {
    padding: 60px 0;
}

.section-title {
    text-align: center;
    margin-bottom: 48px;
}

.section-title h2 {
    font-size: 2rem;
    color: var(--text-dark);
    margin-bottom: 12px;
    font-weight: 600;
}

.section-title p {
    color: var(--text-light);
    font-size: 1rem;
}

.cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 28px;
}

.card {
    background: var(--white);
    border-radius: var(--radius);
    padding: 36px 28px;
    text-decoration: none;
    color: var(--text-dark);
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
    border: 1px solid transparent;
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-hover);
    border-color: var(--primary);
}

.card-icon {
    width: 64px;
    height: 64px;
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
    border-radius: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    margin-bottom: 20px;
}

.card-icon svg {
    width: 32px;
    height: 32px;
}

.card h3 {
    font-size: 1.3rem;
    margin-bottom: 10px;
    font-weight: 600;
}

.card p {
    color: var(--text-light);
    font-size: 0.95rem;
    line-height: 1.7;
}

.page-header {
    background: var(--white);
    padding: 48px 0;
    border-bottom: 1px solid var(--border);
}

.page-header h1 {
    font-size: 2.2rem;
    color: var(--text-dark);
    font-weight: 600;
}

.page-content {
    padding: 48px 0;
}

.tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 32px;
    flex-wrap: wrap;
}

.tab {
    padding: 14px 28px;
    background: var(--white);
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-light);
    transition: all 0.3s;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
    min-height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.tab:hover {
    color: var(--primary);
}

.tab.active {
    background: var(--primary);
    color: var(--white);
    box-shadow: 0 4px 12px rgba(30, 136, 229, 0.3);
}

.subcategory-container {
    margin-bottom: 32px;
}

.subcategory-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
}

.subcategory-btn {
    padding: 12px 22px;
    background: var(--white);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 1rem;
    color: var(--text-dark);
    transition: all 0.3s;
    min-height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.subcategory-btn:hover {
    border-color: var(--primary);
    color: var(--primary);
}

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

.age-selector {
    display: flex;
    gap: 12px;
    margin-bottom: 32px;
    flex-wrap: wrap;
}

.age-btn {
    padding: 16px 32px;
    background: var(--white);
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-dark);
    transition: all 0.3s;
    min-height: 52px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.age-btn:hover {
    border-color: var(--primary);
    color: var(--primary);
}

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

.training-types-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
    gap: 16px;
    margin-bottom: 32px;
}

.training-type-btn {
    padding: 24px 20px;
    background: var(--white);
    border: 2px solid var(--border);
    border-radius: var(--radius);
    cursor: pointer;
    text-align: center;
    transition: all 0.3s;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-dark);
    min-height: 100px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 10px;
}

.training-type-btn:hover {
    border-color: var(--primary);
    color: var(--primary);
    transform: translateY(-2px);
}

.training-type-btn.active {
    background: var(--primary);
    color: var(--white);
    border-color: var(--primary);
}

.training-type-icon {
    font-size: 2.2rem;
}

.videos-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 24px;
}

.video-card {
    background: var(--white);
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: var(--shadow);
}

.video-player {
    background: #1a1a1a;
    aspect-ratio: 16/9;
    position: relative;
    overflow: hidden;
}

.video-player video {
    width: 100%;
    height: 100%;
    display: block;
}

.video-player iframe {
    width: 100%;
    height: 100%;
    display: block;
}

.video-info {
    padding: 20px;
}

.video-info h4 {
    font-size: 1.05rem;
    margin-bottom: 8px;
    font-weight: 600;
}

.video-info p {
    color: var(--text-light);
    font-size: 0.9rem;
}

.no-videos {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-light);
}

.no-videos svg {
    width: 64px;
    height: 64px;
    margin-bottom: 16px;
    opacity: 0.4;
}

.login-container {
    min-height: 80vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 40px 24px;
}

.login-box {
    background: var(--white);
    border-radius: var(--radius);
    padding: 40px;
    box-shadow: var(--shadow);
    width: 100%;
    max-width: 420px;
}

.login-box h2 {
    text-align: center;
    margin-bottom: 32px;
    font-size: 1.6rem;
    font-weight: 600;
}

.form-group {
    margin-bottom: 24px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    color: var(--text-dark);
    font-size: 1rem;
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 14px 18px;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 1.05rem;
    font-family: inherit;
    transition: border-color 0.3s;
    min-height: 50px;
}

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

.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
}

.btn {
    width: 100%;
    padding: 16px 28px;
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
    color: var(--white);
    border: none;
    border-radius: var(--radius-sm);
    font-size: 1.05rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    font-family: inherit;
    min-height: 52px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(30, 136, 229, 0.4);
}

.btn-block {
    display: block;
    width: 100%;
}

.error-message {
    background: #ffebee;
    color: #c62828;
    padding: 14px 18px;
    border-radius: var(--radius-sm);
    margin-bottom: 20px;
    font-size: 1rem;
}

.admin-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 32px;
}

.admin-header h2 {
    font-size: 1.6rem;
    font-weight: 600;
}

.admin-header p {
    color: var(--text-light);
}

.upload-form {
    background: var(--white);
    border-radius: var(--radius);
    padding: 32px;
    box-shadow: var(--shadow);
    margin-bottom: 32px;
}

.upload-form h3 {
    font-size: 1.25rem;
    margin-bottom: 24px;
    font-weight: 600;
}

.admin-videos-list {
    display: grid;
    gap: 16px;
}

.admin-video-item {
    background: var(--white);
    border-radius: var(--radius);
    padding: 20px;
    box-shadow: var(--shadow);
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 16px;
}

.admin-video-info h4 {
    margin-bottom: 4px;
    font-weight: 600;
}

.admin-video-info p {
    color: var(--text-light);
    font-size: 0.9rem;
}

.btn-delete {
    padding: 12px 24px;
    background: #ef5350;
    color: var(--white);
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    transition: all 0.3s;
    font-family: inherit;
    min-height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.btn-delete:hover {
    background: #e53935;
}

.logout-link {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 24px;
    color: var(--text-light);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s;
    min-height: 44px;
}

.logout-link:hover {
    color: var(--accent);
}

.footer {
    background: var(--white);
    padding: 32px 0;
    margin-top: 60px;
    border-top: 1px solid var(--border);
}

.footer p {
    text-align: center;
    color: var(--text-light);
    font-size: 0.95rem;
}

/* 平板端响应式 */
@media (max-width: 1024px) {
    .container {
        padding: 0 20px;
    }
    
    .navbar {
        padding: 10px 0;
    }
    
    .logo-icon svg {
        height: 45px;
    }
    
    .logo-title {
        font-size: 1rem;
    }
    
    .nav-links {
        gap: 24px;
    }
    
    .nav-links a {
        font-size: 0.95rem;
    }
    
    .hero h1 {
        font-size: 2.2rem;
    }
    
    .cards-grid {
        grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
        gap: 24px;
    }
    
    .video-card {
        min-height: 280px;
    }
}

/* 手机端响应式 */
@media (max-width: 768px) {
    html {
        font-size: 15px;
    }
    
    body {
        font-size: 15px;
    }
    
    .container {
        padding: 0 16px;
    }
    
    .navbar {
        padding: 8px 0;
    }
    
    .logo {
        gap: 8px;
    }
    
    .logo-icon svg {
        height: 38px;
    }
    
    .logo-title {
        font-size: 0.9rem;
    }
    
    .logo-subtitle {
        display: none;
    }
    
    .nav-links {
        gap: 16px;
    }
    
    .nav-links a {
        font-size: 0.9rem;
        padding: 8px 0;
    }
    
    .hero {
        padding: 50px 0 40px;
    }
    
    .hero h1 {
        font-size: 1.8rem;
        line-height: 1.3;
    }
    
    .hero p {
        font-size: 1rem;
        padding: 0 10px;
    }
    
    .main-content {
        padding: 40px 0;
    }
    
    .section-title {
        margin-bottom: 32px;
    }
    
    .section-title h2 {
        font-size: 1.6rem;
    }
    
    .cards-grid {
        grid-template-columns: 1fr;
        gap: 20px;
    }
    
    .card {
        padding: 32px 24px;
        min-height: 180px;
    }
    
    .card-icon {
        width: 70px;
        height: 70px;
        margin-bottom: 16px;
    }
    
    .card-icon svg {
        width: 36px;
        height: 36px;
    }
    
    .card h3 {
        font-size: 1.3rem;
        margin-bottom: 8px;
    }
    
    .card p {
        font-size: 1rem;
        line-height: 1.6;
    }
    
    .page-header {
        padding: 32px 0;
    }
    
    .page-header h1 {
        font-size: 1.6rem;
    }
    
    .page-content {
        padding: 32px 0;
    }
    
    .tabs {
        gap: 6px;
        margin-bottom: 24px;
    }
    
    .tab {
        padding: 16px 20px;
        font-size: 0.95rem;
        min-height: 52px;
        flex: 1;
        min-width: 120px;
    }
    
    .subcategory-grid {
        gap: 10px;
    }
    
    .subcategory-btn {
        padding: 14px 18px;
        font-size: 0.95rem;
        min-height: 48px;
        flex: 1;
        min-width: 100px;
    }
    
    .age-selector {
        gap: 10px;
        margin-bottom: 24px;
    }
    
    .age-btn {
        padding: 16px 20px;
        font-size: 0.95rem;
        min-height: 52px;
        flex: 1;
        min-width: 100px;
    }
    
    .training-types-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 14px;
        margin-bottom: 24px;
    }
    
    .training-type-btn {
        padding: 24px 16px;
        font-size: 0.95rem;
        min-height: 110px;
    }
    
    .training-type-icon {
        font-size: 2.5rem;
    }
    
    .videos-grid {
        grid-template-columns: 1fr;
        gap: 20px;
    }
    
    .video-card {
        min-height: 260px;
    }
    
    .video-player {
        aspect-ratio: 9/16;
    }
    
    .video-info {
        padding: 16px;
    }
    
    .video-info h4 {
        font-size: 1.1rem;
        margin-bottom: 6px;
    }
    
    .video-info p {
        font-size: 0.95rem;
    }
    
    .login-container {
        padding: 30px 16px;
        min-height: 70vh;
    }
    
    .login-box {
        padding: 32px 24px;
    }
    
    .login-box h2 {
        font-size: 1.5rem;
        margin-bottom: 28px;
    }
    
    .form-group {
        margin-bottom: 20px;
    }
    
    .form-group label {
        font-size: 1rem;
    }
    
    .form-group input,
    .form-group select {
        padding: 16px 18px;
        font-size: 1.1rem;
        min-height: 54px;
    }
    
    .form-row {
        grid-template-columns: 1fr;
        gap: 20px;
    }
    
    .btn {
        padding: 18px 32px;
        font-size: 1.1rem;
        min-height: 56px;
    }
    
    .btn-delete {
        padding: 14px 28px;
        font-size: 1rem;
        min-height: 48px;
    }
    
    .upload-form {
        padding: 24px;
    }
    
    .admin-video-item {
        flex-direction: column;
        align-items: flex-start;
        gap: 16px;
    }
    
    .admin-video-item .btn-delete {
        width: 100%;
    }
    
    .footer {
        padding: 24px 0;
        margin-top: 40px;
    }
    
    .footer p {
        font-size: 0.9rem;
        padding: 0 16px;
    }
}

/* 小屏手机响应式 */
@media (max-width: 480px) {
    html {
        font-size: 14px;
    }
    
    body {
        font-size: 14px;
    }
    
    .container {
        padding: 0 12px;
    }
    
    .logo-icon svg {
        height: 32px;
    }
    
    .logo-title {
        font-size: 0.85rem;
    }
    
    .nav-links {
        gap: 12px;
    }
    
    .nav-links a {
        font-size: 0.85rem;
    }
    
    .hero h1 {
        font-size: 1.5rem;
    }
    
    .hero p {
        font-size: 0.95rem;
    }
    
    .card {
        padding: 28px 20px;
        min-height: 160px;
    }
    
    .card-icon {
        width: 60px;
        height: 60px;
    }
    
    .card-icon svg {
        width: 32px;
        height: 32px;
    }
    
    .tab {
        padding: 14px 16px;
        font-size: 0.9rem;
        min-width: 100px;
    }
    
    .subcategory-btn {
        padding: 12px 14px;
        font-size: 0.9rem;
        min-width: 80px;
    }
    
    .age-btn {
        padding: 14px 16px;
        font-size: 0.9rem;
        min-width: 80px;
    }
    
    .training-types-grid {
        grid-template-columns: 1fr;
    }
    
    .training-type-btn {
        min-height: 90px;
    }
    
    .video-player {
        aspect-ratio: 9/16;
    }
    
    .login-box {
        padding: 24px 20px;
    }
    
    .form-group input,
    .form-group select {
        padding: 14px 16px;
        min-height: 50px;
    }
    
    .btn {
        padding: 16px 28px;
        min-height: 52px;
    }
}