Before coding full time, I spent my time in biophysics, laser physics, and then laser CVD. By the end of my time as a physicist, I found myself finding excuses to code.
For example, I used OpenCV to perform real-time video analysis. Estimates from OpenCV were then wired in to substrate control which enabled my system to automatically grow very long carbon fibers using laser CVD.
After the transition to full time coding, I helped stand up two successful products, Titan Echo, a tool that helps professional accountants perform cost segregation on commercial buildings, and Blip Billboards, a system that democratizes the display of electronic billboard adds.
When we had our home paid off and a few years of savings, I stepped back to focus my efforts on Brighthike, an app that uses machine learning, spaced repetition and customization to speed up and deepen math education.
All my recent projects have used python/django on the back end. My front end of choice is react/react native. Persistance is managed through postgres.