you could put cheats and challenges in the settings section.
some examples cheats
times 10/100 score. power ups show up much more frequently like 1in 3 chance with stronger effects.
balls are half sized.
balls are bouncer, compress more and increased shot velocity. ect.
challenges
half score. double size balls. no power ups. reduced bounciness. ect.
Viewing post in Aphrodite's Alchemist [Demo] comments
the increase score was (in my mind) in the context of alleviating the grind DEEP into endless but, that's a fair point.
you don't need to implement any specific idea any specific way, those were just things I thought of off the top on my head.
the general idea is you have a mostly unused section in your menu, fill it with togglable option to make the game easier or harder.