Here's how you can write code with codepen using your Mobile phone.

You can code and share your front-end web development projects using CodePen, an online code editor and social development environment. To code and host your projects on CodePen, follow these steps:

1. Visit https://codepen.io/signup to register for CodePen or log in. To start a new project, click the "New Pen" button.
2. Select a starter template or choose the project type you wish to develop (HTML, CSS, or JavaScript).
3. In the CodePen editor, begin writing code for your project. The preview window on the right lets you see your project in advance.
4. When you're finished with the coding, click the "Save" button to save your project.
5. Choose whether you want to make your project public or private, give it a name, and include a description. Your project will be saved when you click the "Save & Close" button.
6. You can share your project with others by copying the project's URL from the address bar.

You can now easily design and test your front-end development projects with CodePen.