... -_- that's because you're no mapper. In the most obvious case, he's talking about he hl engine. Anyway, if you want moving trees, i'd suggest you get some models or have someone model then for you, and with an idle animation that resembles that of a tree standing in the wind. As for cars, and such, i think you'd have to use the func_train and set a path. I'm no entity expert, but that's how i think it's done. If someone cares to elaborate this some further, be my guest.