Grid Layout - CSS - nth child

mixin.less

// this targets 1,5,7,11,13,17,19...
.ale--66 {
    &:nth-child(6n+1),
    &:nth-child(6n+5){
        width:66.666%;
    }
}

// this targets - 2,4,8,10,14,16,20....
.ale--33 {
    &:nth-child(6n+4),
    &:nth-child(6n+2) {
        width:33.333%;
    }
}

.ale--clear__float{
    &:nth-child(3n+1),
    &:nth-child(3n+2) {
        height:200px;
        float: left;
    }
}

.ale--full {
    &:nth-child(3n+3) {
        clear: left;
        width:100%;
        height:300px;

        // bump the height of every other full up to 500px
        &:nth-child(odd) {
           height:500px;
        }
    }
}

aids in producing http://cl.ly/image/2B0V091H3c2c

I was trying to do this, couldn't work it out. You're awesome.