The Delta game emulator offers console emulation from the original Nintendo Entertainment System to the Nintendo 64, including the Sega Genesis|deltagameemulator|Instagram

The Delta game emulator, made by app developer Riley Testut in 2019, ranks No. 1 on the App Store’s free entertainment chart after Apple removed the ban on emulator apps earlier this month.

A game emulator software replicates the functionality of an old gaming console, allowing users to play retro games on modern technology, like the iPhone, in their original format.

However, the legality of using emulators varies based on factors like the ownership of the games and the console copyrights—making downloading or distributing copyrighted games and consoles without authorization illegal in many countries.

The Delta emulator offers console emulation from the original Nintendo Entertainment System to the Nintendo 64, including the Sega Genesis. It is free for iOS users in the US.

Apple’s move comes as the Justice Department filed an antitrust lawsuit against the tech giant last month, alleging the company stalls competition by locking out competing technologies from its iPhone ecosystem. Recently, EU regulators asked Apple to allow non-Apple app stores that already have emulators.