A nice interface where you can switch between the login and signup form, designed by Anna Batura. When you click on the signup button the login panel slides over to the signup section and gives you the option to sign up using an email, name, username and password. Similarly, you can click on the login button to get the option to sign in using the username and password.
If you are having trouble with the pen, try the archived copy on GitHub.
See the Pen Log in / Sign up by @BrawadaCom (@Anna_Batura) on CodePen.0