Funny story, I'm a SWE and my wife used to work as a marketing manager. Her boss wanted her to make something similar, a heat map over a U.S. map. Except he wanted it to work in Excel. She asked me about it and I told her I could code something like that, but no way inside Excel...

Sure enough, she hacked on it for a while and was able to actually build a functioning heat map in Excel. I have no idea how it works. I've been a dev for 20+ years and that remains one of the more voodoo tech things I've seen!