/* 全局样式 */
:root {
    --primary: #4361ee;
    --primary-dark: #3a56d4;
    --secondary: #ff6b6b;
    --dark: #2b2d42;
    --light: #f8f9fa;
    --gray: #6c757d;
    --success: #06d6a0;
    --danger: #ef476f;
    --border-radius: 8px;
    --box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background-color: #f5f7fb;
    color: var(--dark);
    line-height: 1.6;
}

header {
    background-color: white;
    box-shadow: var(--box-shadow);
    position: sticky;
    top: 0;
    z-index: 100;
    padding: 1rem 5%;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--primary);
    display: inline-block;
}

nav ul {
    display: flex;
    list-style: none;
}

nav ul li {
    margin-right: 1.5rem;
}

nav ul li a {
    text-decoration: none;
    color: var(--dark);
    font-weight: 500;
    padding: 0.5rem 0.8rem;
    border-radius: var(--border-radius);
    transition: all 0.3s ease;
}

nav ul li a:hover, nav ul li a.active {
    background-color: var(--primary);
    color: white;
}

nav ul li a.disabled {
    color: var(--gray);
    cursor: not-allowed;
    pointer-events: none;
}

main {
    padding: 2rem 5%;
    min-height: calc(100vh - 150px);
}

footer {
    background-color: white;
    padding: 1.5rem 5%;
    text-align: center;
    color: var(--gray);
    box-shadow: 0 -2px 10px rgba(0, 0, 0, 0.05);
}

.btn {
    display: inline-block;
    padding: 0.8rem 1.5rem;
    background-color: var(--primary);
    color: white;
    border: none;
    border-radius: var(--border-radius);
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    text-decoration: none;
    text-align: center;
}

.btn:hover {
    background-color: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(67, 97, 238, 0.3);
}

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

.btn.primary:hover {
    background-color: #05c090;
}

.btn:disabled {
    background-color: var(--gray);
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

/* 主页样式 */
.hero {
    background: linear-gradient(135deg, #4361ee 0%, #3a0ca3 100%);
    border-radius: var(--border-radius);
    padding: 4rem 2rem;
    color: white;
    text-align: center;
    margin-bottom: 3rem;
    box-shadow: var(--box-shadow);
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.hero p {
    font-size: 1.2rem;
    max-width: 700px;
    margin: 0 auto 2rem;
}

.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.feature {
    background: white;
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    text-align: center;
    transition: transform 0.3s ease;
}

.feature:hover {
    transform: translateY(-10px);
}

.feature .icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

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

/* 登录页面样式 */
.login-container {
    display: flex;
    min-height: 80vh;
    align-items: center;
    justify-content: center;
    gap: 3rem;
}

.login-form {
    flex: 1;
    max-width: 500px;
    background: white;
    padding: 3rem;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
}

.login-form h2 {
    margin-bottom: 0.5rem;
    color: var(--primary);
}

.login-form p {
    margin-bottom: 2rem;
    color: var(--gray);
}

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

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.form-group input {
    width: 100%;
    padding: 0.8rem;
    border: 1px solid #ddd;
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

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

.error-message {
    margin-top: 1rem;
    padding: 0.8rem;
    background-color: #ffebee;
    color: var(--danger);
    border-radius: var(--border-radius);
    display: none;
}

.login-illustration {
    flex: 1;
    max-width: 500px;
    display: flex;
    justify-content: center;
    align-items: center;
}

.illustration {
    width: 100%;
    height: 400px;
    background: linear-gradient(135deg, #a8dadc 0%, #457b9d 100%);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    position: relative;
    overflow: hidden;
}

.illustration::before {
    content: "";
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(255,255,255,0.2) 0%, rgba(255,255,255,0) 70%);
    transform: rotate(30deg);
}

/* 视频列表样式 */
.videos-container {
    max-width: 1200px;
    margin: 0 auto;
}

.videos-container h1 {
    margin-bottom: 0.5rem;
    text-align: center;
}

.subtitle {
    color: var(--gray);
    margin-bottom: 2rem;
    text-align: center;
}

.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 2rem;
}

.video-card {
    background: white;
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--box-shadow);
    transition: transform 0.3s ease;
    position: relative;
}

.video-card:hover {
    transform: translateY(-5px);
}

.video-thumbnail {
    height: 180px;
    position: relative;
    overflow: hidden;
}

.video-thumbnail::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(45deg, #ff9a9e 0%, #fad0c4 100%);
    z-index: 1;
}

.video-lock {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 3rem;
    color: rgba(255, 255, 255, 0.8);
    z-index: 2;
}

.video-number {
    position: absolute;
    top: 1rem;
    left: 1rem;
    background: rgba(0, 0, 0, 0.7);
    color: white;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    z-index: 2;
}

.video-info {
    padding: 1.5rem;
}

.video-info h3 {
    margin-bottom: 0.5rem;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.video-meta {
    color: var(--gray);
    font-size: 0.9rem;
    display: flex;
    justify-content: space-between;
}

/* 播放器样式 */
.player-container {
    max-width: 1000px;
    margin: 0 auto;
}

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

.video-info {
    padding: 1.5rem 2rem;
}

.video-info h1 {
    margin-bottom: 0.5rem;
}

.video-meta {
    color: var(--gray);
    display: flex;
    gap: 0.5rem;
}

.video-wrapper {
    position: relative;
    padding-top: 56.25%; /* 16:9 Aspect Ratio */
}

.video-wrapper video {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: #000;
}

.progress-container {
    padding: 1rem 2rem;
}

.progress-bar {
    height: 8px;
    background: #e9ecef;
    border-radius: 4px;
    margin-bottom: 0.5rem;
    position: relative;
    cursor: pointer;
}

.progress-fill {
    height: 100%;
    width: 30%;
    background: var(--primary);
    border-radius: 4px;
}

.time-display {
    display: flex;
    justify-content: space-between;
    color: var(--gray);
    font-size: 0.9rem;
}

.video-actions {
    padding: 1.5rem 2rem;
    display: flex;
    justify-content: space-between;
}

/* 关于页面样式 */
.about-container {
    max-width: 1200px;
    margin: 0 auto;
}

.about-container h1 {
    margin-bottom: 2rem;
    text-align: center;
}

.about-content {
    display: flex;
    gap: 3rem;
}

.about-text {
    flex: 2;
}

.about-text h2 {
    margin: 1.5rem 0 1rem;
    color: var(--primary);
}

.about-text ul {
    padding-left: 1.5rem;
    margin: 1rem 0;
}

.about-text ul li {
    margin-bottom: 0.5rem;
}

.about-image {
    flex: 1;
}

.image-placeholder {
    height: 400px;
    background: linear-gradient(45deg, #a8dadc 0%, #457b9d 100%);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    position: relative;
    overflow: hidden;
}

.image-placeholder::before {
    content: "";
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(255,255,255,0.2) 0%, rgba(255,255,255,0) 70%);
    transform: rotate(30deg);
}

/* 响应式设计 */
@media (max-width: 768px) {
    header {
        flex-direction: column;
        padding: 1rem;
    }
    
    nav ul {
        margin-top: 1rem;
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .login-container {
        flex-direction: column;
        padding: 1rem;
    }
    
    .login-form {
        margin-bottom: 2rem;
    }
    
    .about-content {
        flex-direction: column;
    }
    
    .video-actions {
        flex-direction: column;
        gap: 1rem;
    }
    
    .video-actions .btn {
        width: 100%;
    }
    
    .hero {
        padding: 2rem 1rem;
    }
    
    .hero h1 {
        font-size: 2rem;
    }
}

.core-value {
            color: red;
            font-size: 16px;  /* 字体16px */
            position: absolute;
            pointer-events: none;
            opacity: 1;
            transition: all 1s ease-out;  /* 1秒动画 */
        }