[oehpr]

I love loopy for the crazy simplicity, it's good just to illustrate the moving pieces. But when you want to model something, the next tool I'd turn to is Insight Maker

Someone ported https://en.wikipedia.org/wiki/World3 to it: https://insightmaker.com/insight/2531/My-World3

So you can do a lot with it. You can even do sensitivity analysis with it! The devs are super responsive, I made a feature request and they implemented it in a day.