Advanced HTML/CSS/Javascript?

I’m pretty well versed in HTML and have a working knowledge of CSS & Javascript but I need a resource for getting some additional hands-on experience with all of them.

The online training courses all seem too basic and very "Hello World"…i’d like something more real world.

just find a problem and then make something to solve it

Find a site that you think is cool and remake it.

I’ve done this, but mimicking code and making sure it works is easy. I want to understand what each of the elements are doing and why they exist. That and the thought process for how things are built.

For example, I understood what overflow: hidden meant, but it wasn’t clear to me what it was doing in different applications. Same went for DIV tags as they’ve evolved over the last several years (i.e. we used to just use <center> for things whereas now you can use a div tag to wrap a container to do the same)

I found this video last night and I feel like it has been the most help i’ve had in this realm in a long time. Essentially i’d like to find more like this but also some that include the javascript/jquery aspects.