Wonder how the difficulty levels are determined for each video?

It's obvious with lower levels like super and beginner, that the language is very limited, slowed down, you got visual cues etc. But I generally wonder whether Pablo has certain guidlines to determine whether the content in each video is still Intermediate, or is now difficult enough to be advanced. I'm aware that there's a lot of overlap between levels and I've found some intermediate videos harder than some advanced ones. So was just wondering if there's some sort of description of what each level should look like, for ex. not using specific complicated grammar structures, avoiding coloquial language or slang.