Nice use of color to try to make a duotone, but there is too much color. You have white, black, green and purple. The image is really nice and sharp, and it is excellent compositionally. However, for all those others who tried to stick with two tones, I can't score this one higher than a 6 as a courtesy to those who really went out of their way to keep their images within the guidelines. In another challenge though this would be a real contender.
For me, your image makes me think I'm looking at two photos because of the very distinct line down the middle. Also, compared with some of the other duotone entries, it's hard for me to really tell if this is duotone or note, due to the cast light spots on the clear chess pieces.