Hofmann illustrated clearly that the perception of depth, space and movement could be captured on an artist's canvas using only color and shape to create visual tension; that representational forms were not necessary. He called this technique, "push and pull."
On this fun site, you can explore for yourself "...how color relationships and placement affect your perception of space." Just click on the artist palette to create, then print your own 8 1/2" x 11" painting. http://www.pbs.org/hanshofmann/push_and_pull_001.html