The game takes elements of stunt-based extreme sports titles (especially the Tony Hawk series), adds an emphasis on platforming, and tops the whole thing with a graffiti tagging mechanic — which is how protagonists Beat, Gum, and the rest of the GGs liberate Tokyo-to from the “overbearing, corporate-controlled police force” that controls it.
Here's the trailer for the original game:
^I remember playing this on Dreamcast. Really good game. I am looking forward to see how this will turn out.