Several of these works are mixed media on wood and have a relief quality to them. Most of these were done in 1989 and 1990. They make use of indigenous American iconography with spiritual concerns, making the most of geometric and organic forms. The Quetzalcoatl theme starts to appear her. His Chupicuaro “Windows to the Mind” painting was featured on national Spanish network TV in a Coca Cola commercial in 1989- 91.
When Castillo started to do minimal art, he was working within the constructs of a “less is more” philosophy but this changed with the late Chupicuaro and Perceptualism, he totally reversed that concept so that now it becomes a “more is less” approach. Castillo is intrigued by what can be done with horror Vacui as it appears on Mayan art and similar to what Mark Toby’s art does with his overall mark making.
Mario Castillo also wanted to create a synthesis between a rational world of symmetry and geometric shapes representing logic and the mind and what he considers to be the polarity to all this - the world of the psyche and the subconscious represented by Biomorphism in all its forms. Stylistically, this work goes beyond the folk art and pre-Columbian influences. Castillo makes reference to Cubism, Expressionism, Pointillism, Surrealism, and Realism with some emphasis on graphic design and certain elements borrowed from comic book art.