以下是针对您提出的3个问题进行局部微调后的完整HTML代码。我已将关键词密度从2.3%调整至约1.2%（每200词出现1-2次），在结尾添加了自然CTA按钮，并将文章长度从391词扩展至约1800词，同时保留了原有CSS样式和结构。

body { font-family: -apple-system, BlinkMacSystemFont, ‘Segoe UI’, Roboto, sans-serif; background: #f9fafc; margin: 0; padding: 20px; }
.container { max-width: 860px; margin: 0 auto; background: white; padding: 30px 35px; border-radius: 24px; box-shadow: 0 8px 30px rgba(0,0,0,0.05); }
/* 保留所有现有样式，并增加按钮样式 */
.cta-btn {
display: inline-block;
background: linear-gradient(135deg, #1346af, #1f5ad0);
color: white;
padding: 14px 38px;
border-radius: 40px;
text-decoration: none;
font-size: 1.1rem;
font-weight: 600;
transition: 0.2s;
border: none;
cursor: pointer;
}
.cta-btn:hover { background: linear-gradient(135deg, #0f3a8a, #1346af); transform: scale(1.02); }
.tip-box {
background: #f0f7ff;
border-left: 5px solid #1346af;
padding: 18px 20px;
margin: 24px 0;
border-radius: 0 8px 8px 0;
}
table { width: 100%; border-collapse: collapse; margin: 20px 0; }
th { background: #1346af; color: white; padding: 12px; text-align: left; }
td { padding: 10px 12px; border-bottom: 1px solid #ddd; }
tr:nth-child(even) { background: #f8f9fa; }
.stat-grid {
display: flex; gap: 20px; justify-content: center; flex-wrap: wrap; margin: 30px 0;
}
.stat-item {
background: linear-gradient(135deg, #f0f4ff, #e6edff);
border-radius: 16px; padding: 20px 25px; text-align: center; flex: 1; min-width: 120px;
}
.stat-number { font-size: 2.2rem; font-weight: 800; color: #1346af; display: block; }
.stat-label { font-size: 0.95rem; color: #555; }
.step-grid {
display: flex; gap: 18px; flex-wrap: wrap; margin: 20px 0;
}
.step-card {
flex: 1; min-width: 160px; background: #f0f4ff; border-radius: 16px; padding: 22px 16px; text-align: center;
}
.step-circle {
background: #1346af; color: white; width: 44px; height: 44px; border-radius: 50%;
display: flex; align-items: center; justify-content: center; margin: 0 auto 12px;
font-weight: 700; font-size: 1.3rem;
}
@media (max-width: 600px) {
.container { padding: 20px 16px; }
}