Yes is no and no is yes

In Bulgaria that is. When I asked the parents if they liked my Christmas presents they both shook their heads. Which I at first thought was a bit...hmmm...straightforward, but kinda appreciated their candor, until I was told that shaking your head means yes. In Bulgarian. When you nod, but only moving your head backwards, not nodding like we do when we mean yes, it means no. How weird is that?!?