for me a casual gamer is someone who occasionally plays games but not for hours upon hours. most of the time people like that also prefer simple games that don't require hours of investment to become any good at (like for example dark souls) but I'm sure there are casual gamers out there that play games like that.
also trying to come up with a strict definition for a casual gamer seems pretty silly to me because it's such a subjective thing. there really isn't a set point of where a person stops being a casual gamer and becomes a hardcore gamer.
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DON~!