Thanks for the guesses so far guys, sorry I don't have much else to go on. This was a LONG time ago, after all.
I do remember elevation changes though, I believe. That may just be past-me romanticizing a game, but in my mind I can see a river with a dark green slope rising away from it.
I'm also all but positive this game came on one of those super old demo discs, like the PSX ones Playstation Magazine used to come with but for the PC, if that helps at all. I'll continue doing my own research, but I figured I might as well throw that all out there.
EDIT: Oh, and if this helps at all, I remember the UI being big. Like "takes up 25% of the bottom of the screen" big.