Some of the obvious departures are internet-enabled features like StreetPass and MiiVerse, and the addition of a 16:9 perspective. Even with the wider horizontal perspective, Shovel Knight retains an accurate vertical resolution, although each of the game's "pixels" are actually 4.5 x 4.5 pixels on a 1080p display. There are also a few colors used that weren't available in the NES color palette. In addition to the NES' 54 possible colors, Yacht Club added 4 more to enable more detail in certain levels and include characters with darker skin tones.
The game also abandons memory limitations, futzes with the number of colors that can be used simultaneously and allows for much larger sprites. One of the best bits in the piece involves Shovel Knight's excellent soundtrack. It's completely authentic to the era ... but only if Shovel Knight were created for the Japanese version of the NES, the Famicom. Some late NES-era cartridges used a chip that offered 3 additional sound channels, allowing games to have richer soundtracks. The western NES "lacked the necessary cartridge connections" for the sound chip, says D'Angelo, "so it's an unfamiliar sound to most western gamers."
Shovel Knight (Review)