Not too much work, either. I once live coded a Brainfuck interpreter in 30 minutes for PyCon IL, and there aren't really any tricks involved, just work, so it should take the average dev that didn't just practice it maybe 2-4 hours: https://www.youtube.com/watch?v=F5P6Q7vs_-Y

I once live coded a vertically centered image in 30 minutes. My coworkers were pretty impressed. We had low standards...

Another time, I read a Brainfuck wikipedia entry for about 30 seconds.

I still haven't recovered.