In 2011, with a team of interns at a Department of Defense contractor, I created a Wi-Fi geolocation app to locate hotspots. It could find the location in 3D space of every hotspot near you in seconds. We made formulas to model signal strength and probable distances. We used machine learning to optimize completion time and accuracy. I was so caught up in the details that it took me months to see it would be used to kill people. What do we do when we discover that we're building something immoral or unethical? How can we think through the uses of our software to avoid this problem entirely?