Hi, just a little comment. When you write at the beginning about What is a CSS unit?, it is good to keep the example you write in the text also in the image so it follows. You are writing about padding so it will be better to have padding in the code example. Other remark would be that you repeat sentence, just exchange "vw" into "vh" and in the text also change width to height >>
vh is a relative unit that is Relative to 1% of the >>width<< of the viewport*.
Otherwise thank you for the article :)