City Energy Analyst is one of the most widely known open-source tools for the analysis of urban energy systems. The very niche software is used in over 20 countries for over a thousand users. I coded the many first lines of City Energy Analyst as part of PhD studies back in 2013, built a community of more than 40 contributors around it as part of my late academic career until 2020 and finally turned it into part of the venture Superurbana (2022-2025). The code is currently maintained by new PhDs at the ETH Zürich.