Time for action – filling in the gaps

1. Add the FillFromAbove() method to the GameBoard class.

   Public Sub FillFromAbove(x As Integer, y As Integer)
     Dim rowLookup As Integer = y - 1
   
     Do While (rowLookup >= 0)
       If GetSquare(x, rowLookup) <> "Empty" Then
         SetSquare(x, y, GetSquare(x, rowLookup))
         SetSquare(x, rowLookup, "Empty")
         rowLookup = -1
       End If
       rowLookup -= 1
     Loop
   End Sub

What just happened?

Given a square to fill, FillFromAbove() looks at the piece directly above to see if it is marked as Empty. If it is, the method will subtract one from rowLookup and start over until it reaches the top of the board. If no non-empty pieces are found when the top of the board is reached, the method does nothing and exits.

When a non-empty piece is found, it is copied to the destination square, and the copied piece is changed to an empty piece. The rowLookup variable is set to -1 to ensure that the loop does not continue to run.

Generating new pieces

We can create a single...