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

body {
    font-family: Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f5f5;
}

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

header {
    background-color: #fff;
    padding: 20px 0;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

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

.logo {
    font-size: 24px;
    font-weight: bold;
    color: #333;
    text-decoration: none;
}

.auth-buttons {
    display: flex;
    gap: 10px;
}

.btn {
    padding: 8px 16px;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 14px;
    text-decoration: none;
    display: inline-block;
    text-align: center;
}

.btn-primary {
    background-color: #1890ff;
    color: white;
}

.btn-secondary {
    background-color: #52c41a;
    color: white;
}

.btn-block {
    width: 100%;
    padding: 12px;
    font-size: 16px;
}

section {
    padding: 40px 0;
}

.course-list {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.course-card {
    background-color: #fff;
    border-radius: 8px;
    padding: 20px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

.course-title {
    font-size: 18px;
    font-weight: bold;
    color: #333;
    margin-bottom: 10px;
}

.course-price {
    font-size: 16px;
    color: #ff4d4f;
    margin-bottom: 15px;
}

.course-detail {
    background-color: #fff;
    border-radius: 8px;
    padding: 30px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.detail-header {
    margin-bottom: 30px;
}

.detail-title {
    font-size: 24px;
    font-weight: bold;
    color: #333;
    margin-bottom: 10px;
}

.detail-price {
    font-size: 18px;
    color: #ff4d4f;
    margin-bottom: 20px;
}

.detail-meta {
    display: flex;
    gap: 40px;
    margin-bottom: 30px;
    font-size: 14px;
    color: #666;
}

.section-title {
    font-size: 20px;
    font-weight: bold;
    color: #333;
    margin-bottom: 15px;
    padding-bottom: 10px;
    border-bottom: 1px solid #e8e8e8;
}

.course-description {
    margin-bottom: 30px;
    line-height: 1.8;
}

.course-outline {
    margin-bottom: 30px;
}

.outline-list {
    list-style: none;
}

.outline-item {
    padding: 8px 0;
    border-bottom: 1px solid #f0f0f0;
}

.back-btn {
    background-color: #666;
    color: white;
    padding: 10px 20px;
    border-radius: 4px;
    text-decoration: none;
    display: inline-block;
    margin-top: 20px;
}

.course-purchase {
    margin-top: 30px;
    padding-top: 20px;
    border-top: 1px solid #e8e8e8;
}

.purchase-info {
    margin-bottom: 20px;
    font-size: 18px;
}

.price-label {
    font-weight: bold;
    color: #333;
}

.price-value {
    font-weight: bold;
    color: #ff4d4f;
    font-size: 24px;
}

.purchase-btn {
    margin-top: 10px;
}

.payment-info {
    margin-bottom: 30px;
    padding: 20px;
    background-color: #f9f9f9;
    border-radius: 4px;
}

.payment-info p {
    margin: 10px 0;
}

.payment-methods {
    margin-bottom: 30px;
}

.payment-options {
    display: flex;
    gap: 20px;
    margin-top: 20px;
}

.payment-option {
    flex: 1;
}

.payment-option input[type="radio"] {
    display: none;
}

.payment-option label {
    display: block;
    padding: 20px;
    border: 2px solid #d9d9d9;
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.3s ease;
    text-align: center;
}

.payment-option input[type="radio"]:checked + label {
    border-color: #52c41a;
    background-color: #f6ffed;
}

.payment-icon {
    font-size: 24px;
    font-weight: bold;
    padding: 20px;
    border-radius: 4px;
}

.alipay-icon {
    background-color: #1677ff;
    color: white;
}

.wechat-icon {
    background-color: #07c160;
    color: white;
}

.payment-actions {
    margin-top: 30px;
}

.auth-form {
    background-color: #fff;
    border-radius: 8px;
    padding: 30px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    max-width: 400px;
    margin: 0 auto;
}

.form-title {
    font-size: 20px;
    font-weight: bold;
    color: #333;
    text-align: center;
    margin-bottom: 30px;
}

.form-group {
    margin-bottom: 20px;
}

.form-label {
    display: block;
    margin-bottom: 8px;
    font-size: 14px;
    color: #666;
}

.form-input {
    width: 100%;
    padding: 10px;
    border: 1px solid #d9d9d9;
    border-radius: 4px;
    font-size: 14px;
}

.form-input:focus {
    outline: none;
    border-color: #1890ff;
    box-shadow: 0 0 0 2px rgba(24, 144, 255, 0.2);
}

.form-hint {
    font-size: 12px;
    color: #999;
    margin-top: 5px;
}

.form-footer {
    text-align: center;
    margin-top: 20px;
    font-size: 14px;
}

.form-footer a {
    color: #1890ff;
    text-decoration: none;
}

.form-footer a:hover {
    text-decoration: underline;
}

@media (max-width: 768px) {
    .header-content {
        flex-direction: column;
        gap: 15px;
        text-align: center;
    }
    
    .auth-buttons {
        justify-content: center;
    }
    
    .course-detail {
        padding: 20px;
    }
    
    .detail-meta {
        flex-direction: column;
        gap: 10px;
    }
    
    .auth-form {
        padding: 20px;
        margin: 0 20px;
    }
}