Star Ferret was my first attempt at building a game engine alone. At that particular time, I wasn’t super strong with C++ (I remember having to call up a friend and ask how to do scope resolution :P). This project taught me a ton about engine design, graphics, networking, physics, algorithmic optimization, and just generally using math to get things done. I also learned quite a bit about animation (though not really skeletal, just simple morphing of vertices) and interpolation along paths. You have to keep in mind, this was my first project right outside of the text based game (in fact literally like one week after).
I won’t kid you by saying the game is fun… it’s really not, but the attempt was well worth the effort.