Animated Grid Boxes

Code from https://fireship.io/lessons/three-responsive-css-grid-layouts/ + change based on comment that simplifies the css down to one rule, but puts some of the info into the html to mark each div with variables for the animiation delay (--i) and the name of the box's grid space (--g)

a
b
c
d
e
f
g
h
i
j
k
l
main