Hi, the project uses imagemaps, not seperate gui elements and the rectengular image is a leftover from the default Ren'py GUI. The original vector files for the project unfortunately were lost when my computer went kaboom last year.
That said, I can't really help you, as I don't know how this template can be converted for Unity, I never used it. But I'm certain there's some way you can replicate the feature.
