Well it depends what you mean by bittersweet, I suppose. I don't mind good endings with "cost," that's fine. I do mind endings where the narration is trying to imply "this is a good outcome" while the result gives you nothing of the such and it'd be a bad ending if not for the cheerful music playing in the background or upbeat narration accompanying it.
I just find it's a very hard ending type to write while making it feel natural, and most things that try fail miserably. In concept it's not that bad but video games in particular I'd be especially skeptical of them having the talent to pull it off in a satisfying way.
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No problem!
This is a cute and pop genocide of love!