Depends on what you mean by regret. I somewhat regret spending my time at companies that were ultimately shutdown or acquired and my code being unceremoniously

Depends on what you mean by regret. I somewhat regret spending my time at companies that were ultimately shutdown or acquired and my code being unceremoniously thrown out, but that isn't really about the code but rather lifestyle/career choice of working for startups. I don't think from a creative or learning perspective I regret any of the actual coding. Sure some of it wasn't great code but that was generally a product of circumstances, generally the value I personally derived from the code was solid. I did made an explicit career choice early on not to go into aviation/avionics because of it's dual-use. Originally being very interested in UAVs before they were cool I did built my own both fixed wing and quad-copter. After spending some time thinking about how my code would inevitably be used if I joined Boeing, Raytheon or Thales though I decided maybe something else would be better.