What is so cool about Zero. I mean, it’s nothing. Zilch. Nada.
I think zero is cool because, for a while, humans weren’t sure if it was a number at all. Back in the day (when people were still getting used to writing “AD” on their checks), the Greeks were all philosophical about the meaning of nothing as a something, while other math-users on the planet were trying all kinds of slashes and stuff to fill the “holes” where we put zeroes now; while others were trying to do math without it altogether, and experiencing hair loss…
But the coolest thing of all seems to be that the lovely donuty shape of zero came from such a meaningful visual image: it’s a drawing of a hole with nothing inside.
Secretly I think they knew even then that donuts had no nutritional value, but they had to commemorate them anyway. Because … donut!