During this period, the team used Havok software when testing both collision and the behavior of destructible elements. Kat's moveset during her navigation and combat used a combination of hand-animated and physics-based movements. The game used Sony's in-house PhyreEngine. The game was designed to run consistently at 30 frames per second, with lower resolution graphics being used to allow both a consistent frame rate and quicker loading for environments. The team worked with Sony to create several graphical tricks, such as false reflections from character eyes during real-time cutscenes and transparent elements in the scenery, to keep the frame rate high while not compromising the game's graphical quality. The final game featured 300,000 polygons per frame, sitting between the standard polygon counts of the PlayStation 2 and the PS3; including shadow elements and other aspects, the polygon count expanded to the point that the team feared they could not maintain a steady frame rate. In response, they devises a type of polygon culling where graphics hidden by other nearer objects had their polygon count greatly decreased, with separate layers of culling for both the in-game camera perspective and its peripheral area, which was further enhanced using the game's ambient occlusion. A version of this system was also applied to the lighting engine, controlling where light and shadow effects needed to be during movement through the environment. Due to the game's graphics and its platform limitations, a special shader system was used for character model lighting so as to preserve both realistic lighting and the cel shaded graphics. Another unique shader was used for the game's pickups, giving them a translucent quality. The result enabled graphical quality comparable to the PS3, as the culling and shader technology worked around the Vita's hardware limitations. Scenario and art The scenario was written by Naoko Sato. The basic story and the script for some scenes were written by Toyama. The central story concept of two rival characters with similar superpowers was taken from comic books of the 1970s, with Toyama comparing the scenario to Hancock, The Bionic Woman and Majokko Megu-chan. The shift to Vita and the consideration of the game's Western market drastically impacted the game's story and presentation. To appeal to as broad a market as possible, the narrative and presentation were modeled after both Japanese anime and Western comic book narratives, in addition to the comic book influences. Despite being a