It's interesting actually that the article doesn't cover animation. Personally I think it's actually one of the most overlooked parts of 'visual design' these days.. animation I think is looked at quite harshly and as an unnecessary flashy aspect, and I think there's a lot of guilt of exceptional misguided use of animation, but I would say today that animation isn't used enough in the right cases, good animation can improve visual confidence with hierarchy and relationship of data and influence users perception of how responsive and well a product appears to react to them. Google have some good guidelines with material design and I think they are only really scratching the surface with what is and isn't good use of animation.