opening sequences

Each film has an opening sequence that reflects the genre of it . The opening sequence is a crucial part of any film , for example the opening sequence of 'Trainspotting' is crucial to the film if a person was to miss the  opening sequence they could become confused as to where the film starting , how it began? It is a fast paced opening and doesn't have any credits and starts during a scene and chops and changes of images whilst having a voice over. Although i found this opening sequence interesting i don't think i would use this idea when creating my opening sequence. Another opening sequence i looked out was Sweeney Todd' this was all credits and images as what the film was to entail the colours where significant black and white and red flashes showing there is blood spilt during the film reflecting on the genre of the film. Office space's opening sequence was the 'norm' that most films have background music credits along with the introduction of a couple of characters.