"Traditional ghost lore states that spirits remain in the physical realm when they have unfinished business. That trope applies to Gravity Ghost's protagonist Iona. Less common are ghost stories about soaring between tiny planetoids to collect stars. So that's new.
It has been described in Internet shorthand as "like a 2D Super Mario Galaxy," but past the physics of elliptical planetary motion there is not a lot of similarity. Where Mario keeps on his toes to avoid traps and enemies, Iona's journey is a more zen-like experience of exploration and self-discovery. Gravity Ghost touches on some more serious themes and is more than just a platformer with unusual physics."