Hey! Thanks for the answer :)
What I mean by "mutators" is "game changers". Like dynamically modify the game's rules to create a slightly different experience. In the case of your game, a mutator could be "the rule isn't to match two identical cards anymore, the rule is to match two different cards instead." Or, another idea might be "Find the yellow card". That kind of stuff.
Imho I believe it would have create the same feeling of confusion and stress you wanted to create, but with a smaller quantity of frustration.
Congrats on making this game Kolaya, You deserve praises ;)