         parent.tile.value =
             type: 'branch'
             children:
-                left: createTile parent, 'vertical', true
-                right: createTile parent, 'vertical', false
+                left: createTile parent, orientation, true
+                right: createTile parent, orientation, false
             content:
                 dom:
                     parent.tile.value.content.dom
                     .attr 'class', 'tael-node-branch'
             layout:
-                split: 'horizontal'
+                split: orientation
                 divider_location: 0.5
     
     parent =

                .attr 'id', 'tael-node-0'
]

newTile = (tiles, parent_id) ->
    # Add a new tile to the `tiles` array.
    setTileClass = (tile, side) ->
        # Set the class of a tile which is represented as a `ref`.

        # child tile.
        parent.tile.value.child = createTile parent, 'siblingless', true
    
    addLeavesToLeaf = (parent, orientation) ->
        # Create two tiles; convert the 'leaf' tile into a 'branch' tile
        # before inserting the two new 'leaf' tiles into the newly-classified
        # 'branch' tile.
