Black Playground house´s site is at the top of a hill, overlooking the ocean from Hermosa Beach, Malpais, Costa Rica. Its geometry is inspired by the curvy lines of the natural context, trying to imitate the environment. Its materiality also creates a direct relationship with its immediate context. The black concrete exterior walls create a background for the green vegetation around it while creating contrast and privacy with the white interior bedroom areas. The sliding glass doors on the second floor social area offer a view of the hills, while the big roof’s wooden finish creates a continuity from the inside to the outside. The openness of this space creates a naturally ventilated and illuminated environment, while solar water heating and rain water harvesting make this house a highly sustainable structure.