Original report, March 3: Before its retail launch in two days, Legend of Zelda: Breath of the Wild received the spotlight treatment in a Wednesday panel at the annual Game Developers Conference. While explaining the high-level concepts driving new ideas in the highly anticipated sequel, Nintendo developers also revealed a unique prototyping system: a fully playable 8-bit Zelda game.
Three key developers on the game (Hidemaro Fujibayashi, Satoru Takizawa, Takuhiro Dohta) kicked off the presentation by showing an apparent alternate version of the original Legend of Zelda game and asked the crowd to "study" the image, which they said would explain the various elements of its session, dubbed "Change and Constant: Breaking Conventions with Breath of the Wild." It included slight sprite tweaks to the original game, with a thinner, lighter-looking tree, a log on a river's shore, and a clear bottle-shaped icon.
from Nintendo used 8-bit Zelda engine to prototype Breath of the Wild [Updated]