When I saw this I got excited. I thought he was actually drawing with Excel expressions as people are known to do with Desmos (e.g. <a href="https://www.desmos.com/calculator/rn58coma0a" rel="nofollow">https://www.desmos.com/calculator/rn58coma0a</a>). But AFAIKT the artist is just using the drawing tools of Excel to make his art. Impressive, but if with math really impressive.