A general request - or suggestion

[FKlusmann]

Thank you all for these courses.

I know how hard it is to write in an instructive manor. Many of the concepts presented here were new to me, and I imagine they were new to others also. In some cases I feel more lost than before. I have found myself copying and pasting without understanding, with the hope that the concepts would become clear as I went on.
May I suggest that when a new concept is presented, a link be included to information about it.
An example would be Penguin step 58. " Position the .eye elements 45% from the top of their parent," The questions in my head is what is the reference point and what is the percentage of? The stack of

's would mean that the eye is a child of “penguin-head”. So I guess that the 45% is down from top of the head and 55% up from the head’s bottom?
A search for clarity (CSS Parent was helpful. “Now the parent selector is nothing but the selector of the parent, it means a top element of all inner elements.” - CSS Parent Selector | How Parent Selector work in CSS with Examples .

Another example is step 72. I have never seen a CSS reference such as “.shirt div {}”
Just a link in that instruction box would have been helpful.

Thank you all again, and thanks for reading this.
– Fred