Very nice International Chess Game. It must contains more Vector and algorithm on here. Great. (You made one mistake : King can only move one only Grid while the Queen can move freedomly. But it does not matter~)
Thanks for the comment! Well, that 'mistatke' is actually castling which I learned from that tutorial as well. Kind of a particular move which will happen only when certain conditions are satisfied.
And I cannot take the credit for the algorithm which is really designed by the other guy (VR With Andrew) who created the whole tutorial video. I highly recommend you to check it out if you are interested. :)