As Fish has worked to figure out how Fez does work, he's removed a lot of features from the game that he began to see as cruft. "There used to be a billion different things in Fez that didn't have to do with the core mechanic of rotation," Fish said. "We used to have the concept of weight: objects had different weights; if a vase was empty you could fill it with water to trigger a switch ... It was nothing to do with flipping between 2D and 3D."
Other lost concepts included health, which Fish resisted removing at first simply because he liked the classic look of a heart meter on the screen. But it wasn't necessary in a game with no enemies. Both the "design by subtraction" mindset and the lack of enemies are inspired by Ico, he said. Fumito Ueda's game design philosophy informed his, as did Ico's "nostalgic, lonely isolation." He also cites Mario, Zelda, and Myst games as inspirations.