I toyed around with Sphere a bit, but RPG 6.5 was where it was at for me. I spent weeks poring over that code, and it was my first encounter with C++. I learned so much, especially from the implementation of the toolkit (tile editor, map editor, etc.). I never was able to compile it myself, though, as I didn't have access to a proper Borland C++ compiler for DOS, but that didn't matter so much as long as I could read the code and see the end result.
