The margin on the chart is very high on the narrow screen.
You can repeat the question on this page.
see: https://github.com/mermaid-js/mermaid/issues/2160

classDiagram
    Animal <|-- Duck
    Animal <|-- Fish
    Animal <|-- Zebra
    Animal : +int age
    Animal : +String gender
    Animal: +isMammal()
    Animal: +mate()
    class Duck{
      +String beakColor
      +swim()
      +quack()
    }
    class Fish{
      -int sizeInFeet
      -canEat()
    }
    class Zebra{
      +bool is_wild
      +run()
    }

经过一番折腾，我的博客支持 Mermaid 图标功能了。

测试Mermaid显示效果。