There are even the occasional backward steps: you can skip over the trailers when watching a film on video, but for some reason you are not allowed to do so when watching a DVD.

• 甚至有时候技术的发展不进反推：你在看录像时可以跳过预告片，但是欣赏DVD时，出于某种原因你不得不耐着性子把它看完。