I will give you a slightly different take. All resources on the web are geared towards beginners. 90% of CSS tutorials start with basics. I am neither advanced nor very basic. For example, I can make CSS for a text box formatting. I can make first level CSS for hacker news website but I cannot implement nested comments. If I search for for CSS tutorials, codeacademy and all start with most basic stuff like syntax thus wasting lot of my time. Also, many tutorials which claim to teach building uber or Airbnb do not even show screenshots upfront.

My point is make a CSS course targeted at developers like me (10+ yrs Java/C++, Good HTML skills). And I will gladly pay $100 for it.