Lesson 15
Can u correct description of example. "p:first-child" -> "p:first-child". I think space it is important.
@Kanpaso, I believe it's the other way around. What's wrong is the answer to the exercise, not the example.
The :first-child selector should come immediately after the parent element, without whitespace.
Whitespace represents the descendant combinator, so no whitespace is allowed inside a compound selector.
Reference:

Actually, @Kanpaso, there's nothing wrong neither with the answer nor the example! I was completely wrong 😅
plate:first-child won't work because it will, in fact, trigger all plates that are a first-child of any element.
It's equivalent to say * > plate:first-child. Not what we are looking for.
By coincidence plate :first-child does work... but because the descendant combinator will point to all first-child elements in both plates. In our case, just our desired orange, as the first plate doesn't have any child.
Judging by the example though, I guess the expected answer here would be plate > orange:first-child, meaning the orange that is a first-child to a plate!
That was an unexpectedly tough one @flukeout!
Lessons learned.

For me, selectors that are written like the examples, don't work. plate:first-child; neither plate :first-child and div plate:first-child
What am I doing wrong?
@mariacrx In Level 15, there are no plates that are also the first child, so plate:first-child will not work.
Are you sure that plate :first-child (with a space) doesn't work? It's working for me and is an acceptable answer because it selects the first-child that is inside a plate element.
plate > orange:first-child is good, and orange:first-child also, when de semicolon is missing.