/* 基础样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'PingFang SC', 'Microsoft YaHei', sans-serif;
    line-height: 1.6;
    background: #f5f5f5;
}

/* 导航栏样式 */
.navbar {
    background: white;
    border-bottom: 1px solid #eee;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    padding: 1rem 0;
}

.nav-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 5%;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
}

.logo-img {
    height: 40px;
    width: auto;
}

.logo span {
    font-size: 1.2rem;
    font-weight: bold;
    color: #333;
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    text-decoration: none;
    color: #333;
    transition: color 0.3s ease;
}

.nav-links a:hover {
    color: #007bff;
}

.nav-links a.active {
    color: #007bff;
}

/* 用户操作按钮样式 */
.user-actions {
    display: flex;
    gap: 1rem;
    align-items: center;
}

.login-btn, .signup-btn {
    padding: 0.6rem 1.5rem;
    border-radius: 50px;
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
}

.login-btn {
    border: 2px solid #007bff;
    background: transparent;
    color: #007bff;
}

.login-btn:hover {
    background: rgba(0, 123, 255, 0.1);
    transform: translateY(-2px);
}

.signup-btn {
    border: none;
    background: #007bff;
    color: white;
    box-shadow: 0 2px 8px rgba(0, 123, 255, 0.3);
}

.signup-btn:hover {
    background: #0056b3;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 123, 255, 0.4);
}

.login-btn:active, .signup-btn:active {
    transform: translateY(0);
}

/* 课程容器 */
.course-container {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 2rem;
}

/* 课程头部信息 */
.course-header {
    display: flex;
    justify-content: space-between;
    background: white;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.course-info {
    flex: 2;
    padding-right: 2rem;
}

.course-info h1 {
    font-size: 1.8rem;
    margin-bottom: 1rem;
    color: #333;
}

.meta-info {
    display: flex;
    gap: 2rem;
    margin-bottom: 1.5rem;
    color: #666;
}

.description {
    line-height: 1.8;
    color: #555;
}

.course-action {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    padding: 1.5rem;
    background: #f8f9fa;
    border-radius: 8px;
}

.price {
    font-size: 2rem;
    font-weight: bold;
    color: #007bff;
}

.enroll-btn, .try-btn {
    width: 100%;
    padding: 1rem;
    border: none;
    border-radius: 4px;
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.enroll-btn {
    background: #007bff;
    color: white;
}

.try-btn {
    background: white;
    border: 1px solid #007bff;
    color: #007bff;
}

/* 课程大纲 */
.course-content {
    margin-top: 2rem;
    background: white;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.chapter {
    margin-bottom: 1.5rem;
}

.chapter h3 {
    margin-bottom: 1rem;
    color: #333;
}

.chapter ul {
    list-style: none;
}

.chapter li {
    display: flex;
    justify-content: space-between;
    padding: 0.8rem;
    border-bottom: 1px solid #eee;
}

.duration {
    color: #666;
}

/* 返回按钮样式 */
.back-button {
    position: fixed;
    left: 20px;
    top: 50%;
    transform: translateY(-50%);
    background: #007bff;
    color: white;
    border: none;
    padding: 12px 20px;
    border-radius: 50px;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    transition: all 0.3s ease;
}

.back-button:hover {
    background: #0056b3;
    transform: translateY(-50%) translateX(5px);
    box-shadow: 0 4px 15px rgba(0,0,0,0.2);
}

.back-button:active {
    transform: translateY(-50%) translateX(0);
}

/* 返回箭头图标 */
.back-button::before {
    content: "←";
    font-size: 20px;
}