This is a gist; this is only a gist - of yr hmbl srvnt Daniel Julian (aka OldBlueBen) learning Markdown formatting.
To make a short story as long as possible... well, I guess it all starts with Will Glynn.
I'm a bit of a PC gamer, you see, and for the past half-year or so, I've been playing Cities: Skylines (aka CSL).
One of the many way cool things about CSL is this: the game has built-in editors for creating maps and things.
Map creation for CSL can begin with heightmaps - files in which greyscale indicates topographical information.