.tree {
  [class^=tree] {
    height:12px;
    background:#0F8A5F;
    margin:0 auto;
  }
  [class^=tree]:nth-child(2n) {
    background:#34A65F;
  }
  .tree-1 {
    width:30px;
  }
  .tree-2 {
    width:50px;
  }
  .tree-3 {
    width:70px;
  }
  .tree-4 {
    width:90px;
  }
  .tree-5 {
    width:110px;
  }
  .tree-6 {
    width:130px;
  }
  .tree-7 {
    width:150px;
  }
  .tree-8 {
    width:170px;
  }
  ._tree {
    width:20px;
    height:55px;
    background:#8a3b16;
    margin:0 auto;
  }
}