It's a well themed and great idle game!
I'm not hating these kind of game, in fact I like the gameplay pretty much but I would be lying to myself if I said it's a great boss rush game as yeah... this game are great on its own but maybe don't fit for boss rush thingy but that's just my own opinion, no offense.
Gameplay wise, it's pretty simple and fun to grind your character and getting stronger but I immediately stop myself before getting too addicted.
I don't really have anything to say as idk if this game can be made challenging or not, so I'll just stop here.
That's all I guess, if I said something wrong or missed something, let me know.