Отталкивание движущегося объекта от границ формы

            Мяч.Left += МячХ
            Мяч.Top -= МячУ

Public Class Form1
    Dim ZWd As Integer = 0
    Dim ZHg As Integer = 0
    Dim ZW As Integer = Me.DisplayRectangle.Width
    Dim ZH As Integer = Me.DisplayRectangle.Height
    Dim sX, sY As Integer
    Dim PB As PictureBox
    Dim IsMinus As Integer = 1
 
    Private Sub Form1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Click
        sX = Int(Rnd() * 10) * IsMinus
        sY = Int(Rnd() * 10) * IsMinus
    End Sub
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Randomize()
        If Rnd() > 0.49 Then
            IsMinus = -1
        End If
        Dim BM As New Bitmap(20, 20)
        Dim G As Graphics = Graphics.FromImage(BM)
        G.SmoothingMode = Drawing2D.SmoothingMode.AntiAlias
        G.FillEllipse(Brushes.Blue, New Rectangle(0, 0, 19, 19))
        G.FillEllipse(Brushes.White, New Rectangle(4, 4, 7, 7))
        PB = New PictureBox With {.Width = 20, .Height = 20, .BackgroundImageLayout = ImageLayout.None, .BackgroundImage = BM, .Top = ZW \ 2 - 10, .Left = ZH \ 2 - 10}
        Me.Controls.Add(PB)
        sX = Int(Rnd() * 10) * IsMinus
        sY = Int(Rnd() * 10) * IsMinus
    End Sub
 
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        If PB.Top < 1 Or PB.Top > ZH - 20 Then
            sY = -sY
        End If
        If PB.Left > ZW - 20 Or PB.Left < 1 Then
            sX = -sX
        End If
        PB.Left += sX
        PB.Top += sY
    End Sub
End Class