Echo JS 0.11.0

So, is the `/` in the style names "valid"?

No its not, the name is replaced with a minified name see slides 13/14.

That button-depressed example is really bad, since that is just replicating :active.

Is the w3schools slide supposed to be sarcastic? (I really hope so...)

Why in the world would I use something like this and not SASS/LESS or even OOCSS which could be managed in a similar way?