From what I watched of the debate, Trump was his usual full of shit self and Biden seemed completely confused half of the time... I don't even know what the point of the debate was because they were just badmouthing each other's resumes as president when I tuned in.
Anyway, anybody who was on the fence about how sharp Biden's mind is can't be any longer. He was quite painful to listen to IMO... I've always had a thing that when I am embarrassed for someone on TV, I have to change the channel. Biden made me change the channel. I don't think Trump won the debate from what I saw, but Biden certainly did not put to rest any concerns about his mind. He only heightened them exponentially IMO.