It's mobile-optimized, and mobile-used. They do have a web app, but you mostly build your website on your mobile device itself.

As a result, you get an especially mobile-friendly site, and Universe gives a suprising amount of customizability.

I really like the tool, my only issues are that it's a bit more expensive than other builders, and they try to sell you on a domain upfront inside of their system, to keep you on their platform.