Impressive work!

I'm curious though, do you design this as you go? Or do you plan it all out first and go from there?

I have a general idea of basic design already in mind, but I make it as I go for the finer details. For example, I knew ahead of time that I was planning to have this mountain pass cut through, with a truss bridge for the higher track and a railroad crossing for the lower track, but the exact position of the truss bridge and the placement of the trees is something I made up as I went.

I see, sounds fun! Seeing the engineering texts, I would have assumed there was some sketches and planning laid out beforehand.

Just a very basic sketch of the general track layout. It was useful in calculating how much track (300 feet) I needed to buy, and the number of turnouts I'd also need. All the landscape and scenery, I made up as I went with the general idea I already had in mind.

Ah very good! Well keep up the good work!