Nice job making your very own Lisp. Everything sounds very true to the era you're going for. I found the editor itself a litte difficult to use but the provided examples were awesome. :)
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Was it by chance the eval results clearing behavior that threw you off? Because that bites me constantly and I'm not sure how to solve it. I wanted to have the results be copyable with the mouse but to disappear on any keypress, but when I'm working quickly it always results in me accidentally trying to do something before it is cleared and it messes me up every time.