The dust has settled a bit on Pokémon FireRed/LeafGreen on the Switch (thanks to Champions) but it’s still awesome to have access to these Gen 3 games on modern hardware and be able to skip the long process of transferring from the original Gen 3 carts all the way up to Gen 9.
Cilerba, however, has taken a different approach to the games and added a randomiser using ACE (Arbitrary Code Execution). It’s something I’ve covered before in games such as Lufia II: Rise of the Sinistrals and Pokémon Red & Blue, including Cilerba’s own Lugia shiny hunt in the Gen 1 games.
For this, he manipulated the game using Pokémon storage and box names to write code in places and change how the game acts as a result. This is a very crude generalisation of what really happens so you should watch the video to hear the more technical explanations.