Enum direction
        upright = 1
        upleft = 2
        downright = 3
        downleft = 4
    End Enum
 
    Function getSteigung(ByVal neuerichtung As direction, ByVal alteSteigung As _
      Point) As Point
        Select Case neuerichtung
            Case direction.upleft
                Dim newy As Integer = -alteSteigung.Y
                Return New Point(alteSteigung.X, newy)
            Case direction.upright
                Dim newx As Integer = -alteSteigung.X
                Return New Point(newx, alteSteigung.Y)
            Case direction.downleft
                Dim newx As Integer = -alteSteigung.X
                Return New Point(newx, alteSteigung.Y)
            Case direction.downright
                Dim newy As Integer = -alteSteigung.Y
                Return New Point(alteSteigung.X, newy)
        End Select
    End Function
 
    Private CurCoordinates As New Point(1, 100)
    Dim steigung As New Point(1, -1)
    Dim currentdirection As direction = direction.upright
 
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Timer1.Tick
        Dim g As Graphics = PictureBox1.CreateGraphics
        g.Clear(PictureBox1.BackColor)
        If CurCoordinates.Y < 0 Then
            steigung = getSteigung(direction.downright, steigung)
            currentdirection = direction.downright
        ElseIf CurCoordinates.X > PictureBox1.Width Then
            steigung = getSteigung(direction.downleft, steigung)
            currentdirection = direction.downleft
        ElseIf CurCoordinates.Y > PictureBox1.Height Then
            steigung = getSteigung(direction.upleft, steigung)
            currentdirection = direction.upleft
        ElseIf CurCoordinates.X < 0 Then
            steigung = getSteigung(direction.upright, steigung)
            currentdirection = direction.upright
        End If
        g.DrawEllipse(New Pen(Color.Black), New RectangleF(CurCoordinates.X + _
          steigung.X, CurCoordinates.Y + steigung.Y, 16, 16))
        CurCoordinates.X = CurCoordinates.X + steigung.X
        CurCoordinates.Y = CurCoordinates.Y + steigung.Y
    End Sub