Jeet author here. I'm not against classes, but I don't think they need to be used for everything.
I recreated your example in about 2 minutes with a much smaller HTML/CSS footprint. Let me know if it helps or you have any further questions about it, but hopefully it gives you a better understanding of Jeet.
If you learn nth-child, you'll have a much nicer time: http://css-tricks.com/how-nth-child-works/
HTML: http://pastie.org/7949308
Stylus:
div
center()
.left_side
span(2,3)
aside
span(1,3)
padding 15px 30px
background rgba(0,0,0,.25)
article
span(1,2)
padding 15px 30px
background rgba(0,0,0,.1)
&:nth-child(3n+2)
background rgba(0,0,0,.2)
&:nth-child(3n+3)
span(1,1)
background rgba(0,0,0,.15)
.full_width
span(1,1)
padding 15px 30px
background rgba(0,0,0,.3)
h1
margin 0 0 10px