Funny... I just "discovered" by self the weirdness of negative numbers and my understanding was pretty much at par with that site explanation :D

Bookmarking it, tks.

Nicely explained but I am not sure I would rely on explanations given by someone who doesn't understand the whole picture at a superior level:

>We can prove this theorem with advanced calculus, that uses theorems I don't quite understand, but let's think through the meaning.