The iOS App Store has a new No. 1 app, and it’s Delta — Game Emulator. Recently unbanned by Apple, the app allows players to emulate games from several different Nintendo systems, even though it isn’t officially backed by Nintendo.

As a report from The Washington Post outlines, Apple recently loosened its App Store restrictions, which allowed game emulators to return to the storefront even though they were previously banned. Emulators populate a murky gray area in the video game industry, as they are fantastic for game preservation, but also give people ways to play games illegally if they find the ROM online.

Delta — Game Emulator, for example, lets users play ROMs of NES, SNES, Nintendo 64, Game Boy, Game Boy Color, Game Boy Advance, and Nintendo DS games. The app also makes it easy to play these games with more traditional game controllers, adds in save states that allow people to save their progress in games that didn’t previously have that function, and allows players to access cheats previously locked to devices like Game Genie, GameShark, and Action Replay, and more.

Although Delta states right on its App Store page that it’s not affiliated with Nintendo, that hasn’t stopped people with Nintendo game nostalgia from flocking to the app to play older games. As a result, it’s reigned as the No. 1 app on the App Store since Apple loosened its restrictions. It also has a very positive 4.9 star user rating.

Nintendo has not yet commented on or responded to the popularity of Delta, but considering its history with Digital Millennium Copyright Act (DMCA) takedowns and hampering game preservation, it’s unknown what exactly the future holds for apps like it on iOS, even with Apple’s now loosened restrictions.