The first Nintendo emulator to land on the App Store and stick following an Apple rule change plays DS, GBA, N64 games for free

gamesradar.com:

A free retro Nintendo game emulator is now live on the Apple App Store, and because of recent changes made to Apple's app review guidelines, it's actually permitted to be on there. Whether Nintendo will take kindly to it is another matter, given its stance that "supporting emulation also supports the illegal piracy of our products."

In case you missed it, earlier this week, Apple made a tweak to its guidelines surrounding "mini apps, mini-games, streaming games, chatbots, plug-ins, and game emulators," which can be found under point 4.7 of its guidelines. From now on, "retro game console emulator apps can offer to download games," although developers "are responsible for all such software offered in your app, including ensuring that such software complies with these Guidelines and all applicable laws."

As such, emulators are officially allowed to be on the App Store, and Delta, developed by Riley Testut, is one of them. It's not the first Nintendo game emulator to be released following the rule changes, as a Nintendo Entertainment System emulator named Bimmy emerged this week before it was pulled by its own developer "out of fear" (via The Verge). 

Delta plays NES games, as well as SNES, Nintendo 64, Game Boy Color, Game Boy Advance, and DS, and the app's description says there's "plenty more to come!" It also comes with a plethora of additional features, including save states, compatibility with cheat codes, and even local multiplayer. While it allows users to play with mobile controls on their devices (and is even compatible with the microphone for certain DS games that require you to use it), it can be paired with physical controllers, including Switch Joy-Con and pro controllers, Xbox, and PlayStation controllers. 

Since Delta is just an emulator, it doesn't come with games pre-downloaded – users are required to import files of them, instead. This is obviously something that may prove to be contentious with Nintendo, which is firmly against its fans downloading