Connect4

Module Module1
    Private Board(,) As Byte = {{0, 0, 0, 0, 0, 0}, _
                                {0, 0, 0, 0, 0, 0}, _
                                {0, 0, 0, 0, 0, 0}, _
                                {0, 0, 0, 0, 0, 0}, _
                                {0, 0, 0, 0, 0, 0}, _
                                {0, 0, 0, 0, 0, 0}, _
                                {0, 0, 0, 0, 0, 0}}
    Private Turn As Byte = 1
    Private Function Vertical(ByVal C As Byte, ByVal R As Byte) As Boolean
        If R > 2 Then
            For i = 1 To 3
                If Board(C, R - i) <> Turn Then Return False
            Next
            Return True
        End If
        Return False
    End Function
    Private Function Horizontal(ByVal C As Byte, ByVal R As Byte) As Boolean
        For i = -3 To 3
            If C + i < 0 OrElse C + i > 6 Then
                Continue For
            Else
                Dim C4 As Boolean = True
                For n = 0 To 3
                    If C + i + n < 0 OrElse C + i + n > 6 Then
                        C4 = False
                        Exit For
                    Else
                        If Board(C + i + n, R) <> Turn Then
                            C4 = False
                            Exit For
                        End If
                    End If
                Next
                If C4 Then Return True
            End If
        Next
        Return False
    End Function
    Private Function Diagonal1(ByVal C As Byte, ByVal R As Byte) As Boolean
        For i = -3 To 3
            If C + i < 0 OrElse C + i > 6 OrElse R + i < 0 OrElse R + i > 5 Then
                Continue For
            Else
                Dim C4 As Boolean = True
                For n = 0 To 3
                    If C + i + n < 0 OrElse C + i + n > 6 OrElse R + i + n < 0 OrElse R + i + n > 5 Then
                        C4 = False
                        Exit For
                    Else
                        If Board(C + i + n, R + i + n) <> Turn Then
                            C4 = False
                            Exit For
                        End If
                    End If
                Next
                If C4 Then Return True
            End If
        Next
        Return False
    End Function
    Private Function Diagonal2(ByVal C As Byte, ByVal R As Byte) As Boolean
        For i = -3 To 3
            If C + i < 0 OrElse C + i > 6 OrElse R - i < 0 OrElse R - i > 5 Then
                Continue For
            Else
                Dim C4 As Boolean = True
                For n = 0 To 3
                    If C + i + n < 0 OrElse C + i + n > 6 OrElse R - i - n < 0 OrElse R - i - n > 5 Then
                        C4 = False
                        Exit For
                    Else
                        If Board(C + i + n, R - i - n) <> Turn Then
                            C4 = False
                            Exit For
                        End If
                    End If
                Next
                If C4 Then Return True
            End If
        Next
        Return False
    End Function
    Private Function Win(ByVal C As Byte, ByVal R As Byte) As Boolean
        If Vertical(C, R) OrElse Horizontal(C, R) OrElse Diagonal1(C, R) OrElse Diagonal2(C, R) Then Return True
        Return False
    End Function
    Private Function PlaceChip(ByVal C As Byte) As Byte
        For i = 0 To 5
            If Board(C, i) = 0 Then
                If Turn = 2 Then Board(C, i) = 2 Else Board(C, i) = 1
                Return i
            End If
        Next
    End Function
    Private Function ColumnFull(ByVal C As Byte) As Boolean
        For i = 0 To 5
            If Board(C, i) = 0 Then Return False
        Next
        Return True
    End Function
    Sub Main()
        While True
            Dim C As Byte = 0
            Console.WriteLine("Player " & Turn & " Pick a Column (1-7)")
            Integer.TryParse(Console.ReadLine, C)
            While C < 1 OrElse C > 7
                Console.WriteLine("Player " & Turn & " Invalid number, Pick a Column (1-7)")
                Integer.TryParse(Console.ReadLine, C)
            End While
            C -= 1
            If ColumnFull(C) Then
                Console.WriteLine("Column full, Pick another Column")
                Continue While
            Else
                Dim Row As Byte = PlaceChip(C)
                PrintBoard()
                If Win(C, Row) Then
                    Console.WriteLine("Player " & Turn & " WON!")
                    Console.ReadKey()
                    Exit While
                Else
                    If Turn = 2 Then Turn = 1 Else Turn = 2
                End If
            End If
        End While
    End Sub
    Private Sub PrintBoard()
        Console.Clear()
        For y = 5 To 0 Step -1
            For x = 0 To 6
                Console.Write(Board(x, y) & " ")
            Next
            Console.Write(vbCrLf)
        Next
    End Sub
End Module