body { font-family: 'Helvetica Neue', Arial, sans-serif; line-height: 1.6; color: #333; max-width: 800px; margin: 0 auto; padding：h1 { color: #2c3e50; font-size: 2.5em; margin-bottom: 20px; } h2 { color: #2980b9; border-bottom: 2px solid #ecf0f1; padding-bottom：10px; margin-top: 40px; } h3 { color: #34495e; margin-top: 30px; } p { margin-bottom: 20px; } ul