It’s a Fan, NOT an AC
This is an ancient project. It was developed around 2004. I could't believe it I could dig up some pictures to show the process. Although the visual language is outdated, the documents cover the major steps. I wasn't paying attention to document a project development process. This one survives only because I wanted to use it as an example in one of my book. So I keep telling my students, document, document, document. I learned this in a hard way