Ask HN: Learning CSS – Are there resources for graded exercises?

When I was learning music, there were graded exercises for progressing. For example Trinity College and the Associated Board (ABRSM) have graded exams for measuring progress when learning a musical instrument.

I've been reading books on CSS, but I was wondering if someone (a CSS expert here) could put together a resource for gradually getting better at advanced CSS related things. More like a series of exercises that take you from one level to another.

In fact for programming we have a lot of sites that allow you to solve problems classified as Easy, Medium or Difficult. A resource like this for CSS would be great. I would be even better if the exercises were classified as grade 1 to grade 8. The idea would be some mockups which would be classified as per difficulty.

Thanks to everyone for inputs in advance.