.tree, .tree ul, .tree li {

    list-style: none;
    margin: 0;
    padding: 0;
    position: relative;

}
  
.tree {

    margin: 0 0 1em;
    text-align: center;

}

.tree, .tree ul {

    display: table;

}

.tree ul {

    width: 100%;
  
}

.tree li {

    display: table-cell;
    padding: .5em 0;
    vertical-align: top;

}
         
.tree li:before {

    outline: solid 1px #666;
    content: "";
    left: 0;
    position: absolute;
    right: 0;
    top: 0;

}

.tree li:first-child:before {left: 50%;}
.tree li:last-child:before {right: 50%;}
  
.tree code, .tree span {

    border: solid .1em #666;
    border-radius: .2em;
    display: inline-block;
    margin: 0 .2em .5em;
    padding: .2em .5em;
    position: relative;

}
         
.tree code {

    font-family: 'Lucida Console', monospace;

}
           
.tree ul:before,
.tree code:before,
.tree span:before {

    outline: solid 1px #666;
    content: "";
    height: .5em;
    left: 50%;
    position: absolute;

}

.tree ul:before {

    top: -.5em;

}

.tree code:before,
.tree span:before {

    top: -.55em;

}
  
.tree > li {margin-top: 0;}

    .tree > li:before,
    .tree > li:after,
    .tree > li > code:before,
    .tree > li > span:before {
    outline: none;

}