using embedded for loops you can easily repeat in 2 dimensions.
using one for loop you can lets say draw 10 circles in a row on the X axis...

oooooooooo

now using a second loop around this loop, you can repeat this row several times to get the following

oooooooooo
oooooooooo
oooooooooo
oooooooooo
....


in this example the i and j value were also used to scale the boxes so they get smaller

Thanks, this is good, but can you explain what is actually happening with the "for" loops?

"int i = margin" creates a variable "i" and sets it to the value of "margin".
"i < height-margin" tells it to keep looping while "i" is less than the value of "height-margin".
"i += box_space" tells each loop to increment "i" by i + "box_space" (I think), usually this is just defined as "i++", which means increment by 1 each loop.