Sub DoBall()

Speed = 5
xFlag = 1
yFlag = 1

If xFlag = 1 Then
Ball.X = Ball.X + Speed
Else
Ball.X = Ball.X - Speed
End If

If yFlag = 1 Then
Ball.Y = Ball.Y + Speed
Else
Ball.Y = Ball.Y - Speed
End If

If Ball.X >= Form1.width Then
xFlag = 0
End If

If Ball.X <= 100 Then
xFlag = 1
End If

If Ball.Y >= Form1.height Then
yFlag = 0
End If

If Ball.Y <= 100 Then
yFlag = 1
End If

End Sub

The above code works when Form property is set to 1-Twip, but when I change it to 3-Pixel the code no longer works. The ball flies of the form. Why? Please help!

Thanks