Responsive animated landing page

In this challenge, I have made some layout/design decisions that I believe have improved the responsive flow a bit.

I have had an issue with a 'side-effect' while implementing fade-in animation on this project, which I described in detail in the README file on my repository link.

Although I have come up with a different solution eventually, I'd appreciate if someone could tell me what specifically could have caused the said side-effect and whether I could have refactored my code to resolve it without adding the extra CSS.

Thanks in advance!