Анимация: шарик отскакивает от стенки - VB

Option Explicit
 
Private Sub Command1_Click()
    Dim x As Single, y As Single, dx As Single, dy As Single
    Picture1.Scale (0, 200)-(100, 0)
    x = 0: y = 0: dx = 0.2: dy = 0.1
    Picture1.AutoRedraw = True
    Picture1.FillStyle = 0: Picture1.FillColor = vbRed
    Do
        Picture1.Cls
        Picture1.Circle (x, y), 2, vbRed
        DoEvents
        x = x + dx
        y = y + dy
        If (x > 100 Or x < 0) Then dx = -dx
        If (y > 200 Or y < 0) Then dy = -dy
    Loop
End Sub
 
Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
    End
End Sub