This is a cool typing text effect that is available in 2 version coloured and black/white. It was designed by Steve Gardner. As you type in the letters are formed by smaller bits fusing together to form each caracter and the reverse of the effect is triggered when you hit backspace.
If you are having trouble with the pen, try the archived copy on GitHub
Letters Typing Effect Snippet
See the Pen Animated Letters by Steve Gardner (@steveg3003) on CodePen.0