Mozilla splach page challenge issue/responsive images chapter non included in html course?

Hi,
I’m a bit confused, and I feel like I’m the only one having the following issue!

So, I’ve been going through the core modules of learn development and I’ve reached the Splash page challenge.
I found in the index.html this comment:

Even though I’ve been following the curriculum without skipping any section, I had no idea what those attributes were.
After googling them I found a MDN a responsive images guide, that I have yet to read well before trying to redo the challenge. (the page is not part of the web development course though)

I found in the github learning area a folder called responsive-images:
Github repo
It contains the images used for the responsive images-guide, but the active learning part of the guide doesn’t make use of those images.
So it makes me think there might have been a chapter previous to this challenge that doesn’t exist anymore.

Another thing, in the brief it is said to create 400px version of some images and it doesn’t mention 120px, which are part of the marking-guide. So I presume there are some information missing in the brief.
I found this video on youtube https://www.youtube.com/watch?v=PyqUkdvGSGY and her brief mention the 120px images.
I haven’t been through the whole video yet, but I’ve also seen a prerequisite section that I cannot see in the actual splash page.
In the video it looks like she knows there is going to be some responsive images problem to solve, but the link she gives in the video brings me to the same course I’m following, with again no responsive-images section, how does she know?

I’m super confused!
Has the learn_web_development been changed? is there a responsive images chapter missing? Has the brief for the Mozilla splash page been changed?
Or is it just part of the game, do I have to scout all the web to do this challenge?
What confuses me even more is that from what I gathered I am the only one having this problem!

Ok, so checking again the yotube video, her brief is completely different from the one I have here:
[Mozilla splach challenge](https://Mozilla splach challenge)Challenge: Mozilla splash page - Learn web development | MDN

Her brief actually tells her she should uses responsive images, and which size for which screen size as well.

What’s going on?
(If I open the page I coded in the browser it looks fine apart from the logo on the top right and corner, which looks funky probably because it should have been 120px instead of the 400px advised in the brief…)

From my understanding the challenge has been changed and simplified, but not the marking-guide on the github repository. Am I right?