This is interesting to me because I separately came up with the "toy" idea in trying to figure out for myself exactly what a "game" is, anyway. Many popular things marketed as "games" really are toys by this standard, in the sense that you have to build your own win conditions around them. I'm thinking here of pretty much the entire simulation genre, as well as even very niche and complex things like Dwarf Fortress.

I'm sure many others have separately come up with this idea, too.