If you could build anything you want, what would it be and why?

(If this was a weekly question and you know the week number off the top of your head, let me know and I just go look there lol.)

I'm just interested to see what people here would build.

@irene congratulations

A 3D modeling and rendering software. I've already started building it, but there's so many hard things to do and my approach is to work alone and never google a solution before spending some day thinking about it. It's more like a learning project. It will take some huge time to complete, but I'm already learning a lot