What kind if (probably Asian) seed was this?

So I was at my local Chinese restaurant and the owners child was eating some seeds and left some on the table that we sat down at. They were mostly black if I remember correctly, and I think they were like red or purple near the center. They were sort of arrow-head shaped I think. The shell was hard, and I don't think I was supposed to eat that part, but the core was sweet and had a distinctive flavor. Any thoughts on what it was?