Stelios Constantinides wanted a good signup form where the form does some smart validation as the user types in and since he could not find one that works as he wanted he created one.
If you are having trouble with the pen, try the archived copy on GitHub. You can read more about why he created this on Medium.
Try username as “stelios” to see validation
See the Pen Better form validations by Stelios Constantinides (@stothelios) on CodePen.0