Kabuki stages and theaters have steadily become more technologically sophisticated, and innovations including revolving stages and trap doors were introduced during the 18th century. A driving force has been the desire to manifest one frequent theme of kabuki theater, that of the sudden, dramatic revelation or transformation. A number of stage tricks, including actors' rapid appearance and disappearance, employ these innovations. The term , often translated as "playing to the gallery", is sometimes used as a catch-all for these tricks. The , and several innovations including revolving stage, and have all contributed to kabuki. The creates depth and both and provide a vertical dimension.