Front-End Challenge from Colt Steele: Stepper Form

In the past weeks I reviewed a bit my front-end (html-css-javascript) lessons, and also found an interesting challenge lately. It is a vanilla js challenge by Colt Steele, published on Youtube:

My solution to it:
https://github.com/zoltanhalasz/StepperForm

Working link(live project):
https://codepen.io/zoltanhalasz/project/editor/ApPwKj

Explanation:
-I am using a structure with div's with classes and id's that can be targeted by Javascript DOM manipulation.
- the script uses lots of functions, and the getElementById used to target the classes/ids
- use hide/show for the stepper form via Javascript (manipulating DOM styles)

Recommended reading:
- Javascript DOM: https://www.w3schools.com/js/js_htmldom.asp
- CSS/Html: https://www.w3schools.com/html/default.asp