（2）空位处理函数：empty_do(pic1，pic2)

Private Function empty_do(pic1 As PictureBox, pic2 As PictureBox)

Dim a, b As Integer

'以下代码判断是否与无图像的图片框相邻，若相邻则交换

If (pic1.Left = pic2.Left) Then

    If (pic1.Top - pic2.Top = 1500 Or pic1.Top - pic2.Top = -1500) Then

       Call jiaohuan(pic1, pic2)

       b = 1

     End If

ElseIf (pic1.Top = pic2.Top) Then

    If (pic1.Left - pic2.Left = 1500 Or pic1.Left - pic2.Left = -1500) Then

       Call jiaohuan(pic1, pic2)

       b = 1

    End If

End If

'以下代码判断是否完成游戏，若完成则显示成功信息

If (start = 1 And b = 1) Then

    a = 0

    While (a < 9 And Picture1(a).Left / 1500 = Int(a / 3) And Picture1(a).Top / 1500 = a Mod 3)

        a = a + 1

    Wend

    If (a = 9) Then

       Timer1.Enabled = False

       MsgBox "恭喜你取得成功！请再接再厉！", , "祝贺"

       start = 0

       Command1(0).Caption = "开始游戏"

    End If

End If

End Function