A three dimensional shape form and shape can also be described as either organic or geometric.
Working with the reversal of positive and negative space to create complex illusions then Symmetry often feature interlocking images that play with our perception of what is foreground and what is background Perception of form and shape are conditioned by our ingrained "instinct" to impute meaning and order to visual data. When we look at an image and initially form an impression, there is a tendency to latch on to that conclusion about its meaning, and then ignore other possible solutions. This may make it hard to see the other images. Training the eye to keep on looking beyond first impressions is a crucial step in developing true visual literacy.