Not so long ago you needed to download specific emulation apps in order to somehow get retro video games playable on your smartphone. These apps and methods were often unreliable and came with the dark spectre of copyright law hanging over them.
Those days were the times when only the truly dedicated retro gamer would venture down the path of downloading emulators, configuring them to work and then sourcing the roms for the games. It was never a straight forward process and one that often left you feeling a bit short changed at the end as the games weren’t necessarily formatted for a smartphone screen and touch screen controls.