We're very happy to hear you like the art choices that our artists have made, they're doing a great job.
To answer your question about the progress bar, It indeed will unlock certain abilities and gameplay elements the further it progresses.
We are still working on some of our gameplay mechanics. Over the course of the coming few weeks almost all of our planned mechanics should be added to the main build. So we hope you will enjoy those as they get added.
As always, we greatly appreciate both your interest in our project as well as the input and feedback you give us.