a half-written computer game doesn't run at all
I realize this does not really address your main point, but you can have half-written games that do run. I've been writing a game on and off for the last couple of years, and it's been playable the whole time. Make the simplest possible underlying engine first, so it's playable (and testable) as soon as possible.
This seems like a really good concept to keep in mind. I wonder if it could be applied to other fields? Could you make a pot that remains a pot the whole way through, even as you refine it and add detail? Could you write a song that starts off very simple but still pretty, and then gradually layer on the complexity?
Your post inspired me to try this with writing, so thank you. :) We could start with a one-sentence story: "Once upon a time, two lovers overcame vicious prejudice to be together."
And that could be expanded into a one-paragraph story:...
r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.