Although the creators of Hollow Knight Silksong have prepared many difficult challenges, this turned out to be not enough for some hardcore fans.
A modder with the nickname TheWackyKnight introduced "Hollow Knight Death Swap - Silksong". The idea of the project is simple: depending on the selected setting, when dying or taking damage in one game, the user instantly switches to another.
The player HandowShandowed went a little further and fought two bosses simultaneously in Silksong and Hollow Knight (without switching between games — one controller sent signals to both).