for the characters they had designed in advance, for The Last Guardian they made Trico as flexible as possible, allowing them to create levels and have Trico adapt to them. The size difference and interactions between the boy and Trico were informed by the limitations of the PlayStation; if the characters were of the same size, the team would have needed to determine the animation interactions for both, whereas Trico's size meant the boy's animations would not need to affect him much. Although the boy is less detailed than Trico, he was animated via key frame animation. He places hands on nearby walls, and reaches to pet Trico without player interaction. Ueda felt these animations were necessary to help convince the player of the game world. The animation system uses layers of animation that mimic real-life physics, taking advantage of the greater processing power of the PlayStation 4. The team considered making the player character a girl, but felt it would not be realistic that a female character would have enough stamina to climb Trico. To create the game's art and architecture, the team used the same "design through subtraction" method they had used to develop Ico and Shadow of the Colossus, removing elements they felt distracted from the core experience. Music is used sparingly to highlight key emotional moments, such as when Trico uses his tail to catch the boy as he falls from a collapsing platform. The game uses vertical space to emphasize the boy's small size. The Last Guardian game engine builds on the team's previous development of AI processing from Ico and transformative collisions from Shadow of the Colossus. It is the first Team Ico game to use a full physics engine, Havok. According to Ueda, the effect of wind was modeled separately for each of Trico's feathers. Yasuhide Kobayashi, vice president of Japan Studio, stated that the title The Last Guardian was chosen to appeal to the larger demographic markets in the United States and Europe for the PlayStation 3, hoping to avoid the cultural problems in title and artwork blamed for Icos low sales in western countries. In August 2019 interview Fumito Ueda mentioned that Trico they were creating on PlayStation 3 actually had more motion patterns than the PlayStation 4 version did, but they were unable to transfer everything due to transition time issues. Technical development With initial ideas for The Last Guardian