Op Art can be defined as a type of abstract or concrete art consisting of non-representational geometric shapes which create various types of optical illusion. For instance, when viewed, Op Art pictures may cause the eye to detect a sense of movement (eg. swelling, warping, flashing, vibration) on the surface of the painting. And the patterns, shapes and colours used in these pictures are typically selected for their illusional qualities, rather than for their substantive or emotional content. In addition, Op artists use both positive and negative spaces to create the desired illusions.