Mark A. Reynolds is devoted to developing geometry as an art form. Not surprisingly, many of his hand-drawn works and paintings involve diagonals and diagonal relationships. His works have been produced during the 21st century, so in that regard, his output and explorations are an "offspring" of the Phenomenon of Diagonality that occurred in the 20th century.

True to a core feature of Diagonality in its purest form of expression, Reynolds' drawings and paintings are often not symmetrical; he revels in asymmetrical relationships. This gives his work a dynamism and motion that is truly modern. And yet he works with geometric relations that go back to ancient Greece and even further back to ancient Egypt.

As Reynolds writes, "Some of the artwork is based on discoveries and inventions that I have made through the daily practice of drawing and experimentation. The work develops as much from an artistic and creative process as from any pre-planned calculations, although the perimeter ratio is always predetermined in order to define the specific geometric system I will be working with. It is through an organic process of overlays, tracings, revisions, exploration, and experimentation with geometric systems – specifically, certain ratios and proportioning systems found in rectangles, squares, and triangles – that I have been able to produce the drawings and paintings presented here."

The octagon has been central to the unfolding of Diagonality through the ages. Based on what has survived through history, the earliest use of the octagon in architecture is the Tower of the Winds still standing in Athens, Greece. It was a dominant geometric architectural motif during the Romanesque period and Gothic era. It was heavily used through the Renaissance, which is the period that Mark Reynolds turns to, particularly the drawings and designs of Leonardo da Vinci.

On his website (markareynolds.com), in the article, The Octagon in Leonardo's Drawings, Reynolds reveals the depth of his research as he writes, "The construction demonstrates that Leonardo’s explorations were far more than rudimentary. A drawing for the plan of the city of Imola, in 1502 (Windsor, RL 12284) shows a plan view of the city drawn in a circle divided into eight parts (with four subdivisions of each of the eight sections). Several drawings of octagon-based fortifications done in 1504 can be found in Cod. Atl. folio 48, v-a. Cod. Atl. f 286 r-a, of technological studies and wooden architecture (an “anatomy theatre”?), shows a circle divided into eight parts, each containing its own circle. There is also a famous sheet of sketches for the Last Supper and geometrical drawings in the Royal Library (Windsor RL, 12542)."