A fun little thought experiment. Type Inversions
There are 18 pokemon types, so there are three ways I see it going.
The simplest way would be in 9 pairs. Like Fire and Ice. And you go down the groups making sets.
Another possible way would be to make 6 trios to rotate around. Like Flying, Electric, and Ground.
The most complicated method would be to make a train of shifts, incorperating all the types in a long chain. Each tyoe change moving into another.
To keep it simple, and because I think it provides more contrast, I like the idea of using the first option. So as an example set.
Bug -> Rock (Small Bug and Big Boulder)
Dark -> Fighting (Evil and Good/Honorable)
Dragon -> Normal (Extraordinary and Ordinary)
Electric -> Ground (Lighting from the Sky and The ground or digging under)
Fairy -> Steel (Fantasy and Science Fiction)
Fighting -> Dark
Fire -> Ice (polar opposites, Heat and Cold)
Flying -> Psychic (Bird Brain and Super Smart)
Ghost -> Grass (Life and Death)
Grass -> Ghost
Ground -> Electric
Ice -> Fire
Normal -> Dragon
Poison -> Water (Toxicity and purity)
Psychic -> Flying
Rock -> Bug
Steel -> Fairy
Water -> Poison
I'd be curious what other people think. I'm sure there are lots of ways this could be broken down. Like how this example doesn't have Psychic and Fighting as a pair despite it being an iconic pairing.
Imagine an inversion portal opened, and on the other side is an inverted world with the same pokemon from that region have their types changed. Some see minor change depending on how thongs are inverted. Like in my system Qwilfish doesn't see change. But Durant and Carbink would trade typings.