The Legend of Zelda: Breath of the Wild is the most advanced entry in the series yet, but in the early stages of development, Nintendo used a 2D prototype based on the original Zelda on NES. Nintendo Wire recently had a similar idea, and they've created a prototype for a retro re-imagining of Breath of the Wild as a Game Boy Color title in the vein of Oracle of Seasons and Oracle of Ages.
The two minute clip shows off the opening moments of Breath of the Wild re-imagined in a throwback 8-bit style. This includes a look at the Shrine of Resurrection and the iconic scene of Link walking out onto an outcropping and surveying Hyrule below. They also included a map of Hyrule, an item screen, the Old Man, and the outside of the first shrine. It's a surprisingly detailed effort, and they even created an accompanying game manual!
Check it out above!