SASS, JS, appendChild(), BEM, keyframes, flexbox e etc

Hello guys. This is an improvement to this challenge with fixes and various additions. I structured my HTML using the BEM methodology to be more organized. I added a pseudo preload page with custom presentation with my name. Replaces the Careers button with the Theme button, through which it is possible to choose 3 different themes from the page I created, being Normal, Futuristic and Elegant and each one with its respective customization. The futuristic theme has an animation built with SASS and creation of divs with JS appendChild(). Each theme has its distinct letters (fonts). I really liked the end result I got. There will definitely be bugs and improvements to be made. Hugs.