I've skimmed the source.
You are already using a struct for the lemming. You can implement what I have suggested with all-public structs and normal functions. I.e., you don't need inheritance, you don't need virtual methods, ...
This is a general observation: A language is a toolbox, you don't need to use every tool.
For readable source, try to keep your identifier names in English. Comments in English are also preferred.
-- Simon