For this 484-square-foot rear add-on, dubbed the Tetris Extension, architect and photographer Jaime Diaz-Berrio paired up with architect Mark Allan of Crosshatch to combine strong, interlocking shapes to incorporate a new bedroom, bathroom, and central living lounge. The house’s original Californian bungalow facade was retained, so the modern extension is not visible from the street, and only reveals itself as the user walks through the old house.