/* the root block in the tree */
div.tree {
    width: 100%;
}

/* each sub block in the tree, one for each branch */
div.subtree {
    margin-left: 1em; /* indent */
    
}

/* all nodes in the tree have the class tree-node */
div.tree-node {
    
}

/* a tree node that has children have this class */
div.tree-branch {

}

/* a tree node that have no children has this class */
div.tree-leaf {
    
}