Animation for brow grain game?

Question

css

Hello. I want to make something like a browser game, but I didn’t get a clear answer from Google to the question: “How to make animation”.
Maybe because before he was only doing back-end. Who has the experience of creating something like this, share the way :)
So far I have only done authorization, user profiles and similar goodies.
Gitgub: https://github.com/YuriyKlepka/website?files=1