The Kanto Expansion Pak is a ROM hack of Pokémon Red that expands the chromatic generation with scrapped Pokémon, regional variants, and cross-gen evolutions. It attempts to remain as faithful as possible to the game's design specification while doing this, ensuring that RBY OU does not deviate significantly from its roots. Thus, it doesn't include generational gimmicks like Mega Evolution, it simply aims to port what is technically possible in a vanilla Gen 1. It also aims to be compatible with any Gen 1 metagame, allowing tiers like Monotype, LC, NFE, Nintendo Cups, and more to be at least playable for the average user. The original Pokémon are left completely unchanged and balanced around.