Decorations were usually copied from books and applied by native artists. The religious designs and paintings are said to ""show the flavor of the Spanish Era, mixed with the primitive touch of the Indian artists"." The impact that mission architecture has had on the modern buildings of California is readily apparent in the many , commercial, and residential structures which exhibit the tile roofs, arched door and window openings, and stuccoed walls that typify the "mission look." These elements are frequently included in the exterior finish of modern buildings in California and the Southwest, and are commonly referred to as Mission Revival Style architecture. The inclusion of these features in whole or part into otherwise ordinary commercial buildings has been met with varying levels of acceptance, and is regarded among some critics as ""mission impossible"", a phenomenon that is seen most brashly in the fast food emporiums of Taco Bell. When well-done, a mission style building will convey an impression of simplicity, permanence, and comfort, with coolness in the heat of the day and warmth in the cold of night (due to a phenomenon known as the thermal flywheel effect).