It's not just a basic HTML site. That's just what your Browser gets to see.
I haven't looked at the site codes in detail (read: at all), but I assume most of the pages are server-generated. This means, everytime you click on a Gleemax link, your computer connects to the server, the server checks reads the link and gathers what you wants, and creates a HTML page - on the fly - to give you the content you asked for.
In this Alpha state, I assume they concentrated more on the Server giving you the correct content and having sensible strategies for handling multiple requests, getting information out of their data base efficiently and so on. They apparently did care less about the templates that are used to generate the "look and feel" of a site and formats the content in a nice format.
That's not saying that they couldn't be a lot better, but at this point, they haven't just gone around doing it. Maybe the clever web designers are still developing good templates - or they are still busy with other stuff, because there are no designated designers just for the look & feel (it would certainly better if there were some, but this depends a lot on the budget and time constraints they are under. And maybe they are just not enough to have finished their designs at this state, and are still trying to work out to combine their cool design stuff with the content in a clever way.)