>>51021810It's actually even more specific than "state-of-being", "isn't it" agrees specifically with the verb earlier in the sentence being "is". Similar things happen with "will" and "was", and basically all other verbs use "do" at the end for that sort of phrase. For example:
"I speak English, don't I?"
"She hates the game, doesn't she?"
"The game will end, won't it?"
"It's a shitty game, isn't it?"
"That was fun, wasn't it?"
