3) Time Travel
Time-traveling and electronic circuits were initially part of the setting. Shigeru Miyamoto has gone on record saying that the original plans for The Legend of Zelda included time travel between a past and present Hyrule. Link was originally collecting electronic circuits; each called a Triforce and the name Link was used because the main character was originally designed to be a link between the past and the present Hyrule. Latter games of the series have touched on all of these things. Time travel was used quite heavily in The Legend of Zelda: Ocarina of Time and nearly all of the Zelda games hint at a use of technology that is more modern than the medieval setting that the game seems to live in.