俄罗斯方块能否下降 vb版问题

源码如下，主要问题是downable这个函数写的好像有问题，代码上写的是判断四个方块的每一个的下一个的填充色是否为黑色，用的是and，但and用的话又不对，用or又出问题，高手看一下：
Private n(3), m(3) As Integer
Private situation, situation2, linenum, t As Integer

Private Sub Form_Load()
downtimer.Enabled = False
timetimer.Enabled = False
start.Enabled = True
For i = 1 To 199
Load Shape(i)
Next i
For i = 0 To 199
        Shape(i).Left = (i Mod 10) * Shape(0).Width + Shape(0).Left + 10 * (i Mod 10)
        Shape(i).Top = (i \ 10) * Shape(0).Height + Shape(0).Top + 10 * (i / 10)
        Shape(i).Visible = True
    Next i
For i = 4 To 36                                                     '创建预览区的方块
        Load Shape1(i)
    Next i
    For i = 4 To 36                                                     '在预览区排列方块
        Shape1(i).Left = ((i Mod 10) - 3) * Shape1(3).Width + Shape1(3).Left + 10 * (i Mod 10)
        Shape1(i).Top = (i \ 10) * Shape1(3).Height + Shape1(3).Top + 10 * (i / 10)
        Shape1(i).Visible = True
    Next i
Randomize
loadfangkuai
showfang 1
End Sub

Private Sub start_click()

downtimer.Enabled = True
timetimer.Enabled = True
start.Enabled = False

If guantxt.Text <> "" Then
  downtimer.Interval = 1000 / Val(guantxt)
Else: downtimer.Interval = 1000
End If
For i = 0 To 3
n(i) = m(i)
Next i
situation = situation2
End Sub
Private Sub downtimer_Timer()
If guantxt.Text <> "" Then
  downtimer.Interval = 1000 / Val(guantxt)
  End If
hidefang 0
If downable = True Then
For i = 0 To 3
n(i) = n(i) + 10
Next i
showfang 0
Else
      showfang 0
      clearline
      For i = 0 To 3                                                   '引用预览区已经产生的方块
            n(i) = m(i)
        Next
        showfang 0

        situation = situation2

        hidefang 1                                                       '清空预览区
        loadfangkuai                                                     '继续在预览区产生方块
                                                     '继续在预览区产生方块
        showfang 1

End If
scoretxt.Text = linenum * 100



End Sub
Private Sub loadfangkuai()                                            '定义随机产生一种方块的过程
     End Select
End Sub
Private Sub hidefang(a As Integer)
Select Case a
Case 0
      Shape(n(0)).FillColor = RGB(255, 255, 255)
      Shape(n(1)).FillColor = RGB(255, 255, 255)
      Shape(n(2)).FillColor = RGB(255, 255, 255)
      Shape(n(3)).FillColor = RGB(255, 255, 255)
Case 1
      Shape1(m(0)).FillColor = RGB(255, 255, 255)
      Shape1(m(1)).FillColor = RGB(255, 255, 255)
      Shape1(m(2)).FillColor = RGB(255, 255, 255)
      Shape1(m(3)).FillColor = RGB(255, 255, 255)
End Select
End Sub
Private Sub showfang(a As Integer)
Select Case a
Case 0
      Shape(n(0)).FillColor = RGB(0, 0, 0)
      Shape(n(1)).FillColor = RGB(0, 0, 0)
      Shape(n(2)).FillColor = RGB(0, 0, 0)
      Shape(n(3)).FillColor = RGB(0, 0, 0)
Case 1
      Shape1(m(0)).FillColor = RGB(0, 0, 0)
      Shape1(m(1)).FillColor = RGB(0, 0, 0)
      Shape1(m(2)).FillColor = RGB(0, 0, 0)
      Shape1(m(3)).FillColor = RGB(0, 0, 0)
      For i = 3 To 36
      If Shape1(i).FillColor = RGB(255, 255, 255) Then
      Shape1(i).Visible = False
      End If
      Next i
      End Select

End Sub
Private Function downable() As Boolean                             '自定义函数，确定方块是否能下降
    If n(0) < 190 And n(1) < 190 And n(2) < 190 And n(3) < 190 Then
        If Shape(n(0) + 10).FillColor = RGB(225, 255, 255) Or _
           Shape(n(1) + 10).FillColor = RGB(225, 255, 255) Or _
           Shape(n(2) + 10).FillColor = RGB(225, 255, 255) Or _
           Shape(n(3) + 10).FillColor = RGB(255, 255, 255) Then
            downable = True
        Else: downable = False
        End If
    Else: downable = False
    End If
End Function
Private Function leftable() As Boolean                                 '自定义函数，确定方块是否能左移
    If n(0) Mod 10 <> 0 And n(1) Mod 10 <> 0 And n(2) Mod 10 <> 0 And n(3) Mod 10 <> 0 Then
        If Shape(n(0) - 1).FillColor = RGB(255, 255, 255) And _
           Shape(n(1) - 1).FillColor = RGB(255, 255, 255) And _
           Shape(n(2) - 1).FillColor = RGB(255, 255, 255) And _
           Shape(n(3) - 1).FillColor = RGB(255, 255, 255) Then
            leftable = True
        Else: leftable = False
        End If
    Else: leftable = False
    End If
End Function
Private Function rightable() As Boolean                                 '自定义函数，确定方块是否能右移
    If n(0) Mod 10 <> 9 And n(1) Mod 10 <> 9 And n(2) Mod 10 <> 9 And n(3) Mod 10 <> 9 Then
        If Shape(n(0) + 1).FillColor = RGB(255, 255, 255) And _
           Shape(n(1) + 1).FillColor = RGB(255, 255, 255) And _
           Shape(n(2) + 1).FillColor = RGB(255, 255, 255) And _
           Shape(n(3) + 1).FillColor = RGB(255, 255, 255) Then
            rightable = True
        Else: rightable = False
        End If
    Else: rightable = False
    End If
End Function

Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)         '键盘事件
hidefang 0
    Select Case KeyCode
    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    Case vbKeyLeft                                                       '点击向左键
           If leftable = True Then
            For j = 0 To 3
                n(j) = n(j) - 1
            Next j
         End If
        showfang 0
    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    Case vbKeyDown                                                       '点击向下键
         If downable = True Then
            For j = 0 To 3
                n(j) = n(j) + 10
            Next j
        End If
        showfang 0
    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    Case vbKeyRight                                                      '点击向右键
      If rightable = True Then
            For j = 0 To 3
                n(j) = n(j) + 1
            Next j
     End If
        showfang 0
    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    Case vbKeyUp                                                     '点击旋转键（向上键）
        showfang 0
        zhuan
    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    Case Else
        showfang 0
    End Select
End Sub

Private Sub clearline()
For i = 19 To 0 Step -1
       If Shape(i * 10 + 0).FillColor = RGB(0, 0, 0) And _
           Shape(i * 10 + 1).FillColor = RGB(0, 0, 0) And _
           Shape(i * 10 + 2).FillColor = RGB(0, 0, 0) And _
           Shape(i * 10 + 3).FillColor = RGB(0, 0, 0) And _
           Shape(i * 10 + 4).FillColor = RGB(0, 0, 0) And _
           Shape(i * 10 + 5).FillColor = RGB(0, 0, 0) And _
           Shape(i * 10 + 6).FillColor = RGB(0, 0, 0) And _
           Shape(i * 10 + 7).FillColor = RGB(0, 0, 0) And _
           Shape(i * 10 + 8).FillColor = RGB(0, 0, 0) And _
           Shape(i * 10 + 9).FillColor = RGB(0, 0, 0) Then
           For j = 0 To 9
           Shape(i * 10 + j).FillColor = RGB(255, 255, 255)
           Next j
           linenum = linenum + 1
           For k = i * 10 - 1 To 0 Step -1
           If Shape(k).FillColor = RGB(0, 0, 0) And Shape(k + 10).FillColor = RGB(255, 255, 255) Then
            Shape(k).FillColor = RGB(255, 255, 255)
            Shape(k + 10).FillColor = RGB(0, 0, 0)
           End If
           Next k
           clearline
         End If

  Next i
End Sub
Private Sub timetimer_Timer()
t = t + 1
timetxt = t
End Sub
大家主要看这段的代码：
Private Function downable() As Boolean                             '自定义函数，确定方块是否能下降
    If n(0) < 190 And n(1) < 190 And n(2) < 190 And n(3) < 190 Then
        If Shape(n(0) + 10).FillColor = RGB(225, 255, 255) and _
           Shape(n(1) + 10).FillColor = RGB(225, 255, 255) and _
           Shape(n(2) + 10).FillColor = RGB(225, 255, 255) and _
           Shape(n(3) + 10).FillColor = RGB(255, 255, 255) Then
            downable = True
        Else: downable = False
        End If
    Else: downable = False
    End If
End Function

这个软件运行后的界面：
         --------------------编程问答-------------------- 应该先将当前物体擦除后再进行判断。
比如正方形的物体，上面一行将要落下的格子就是下面一行的当前位置，不是黑色。

其他动作的判断也一样要先擦除再判断。 --------------------编程问答-------------------- 单步调试和设断点调试是程序员必须掌握的技能之一。
--------------------编程问答-------------------- 你要注意当前小块下面那小块可能是你当前大块的一部分，此时即使其颜色不是背景色，当前大块也可能能下移。 --------------------编程问答-------------------- 应该将数据和界面分开来处理。所谓数据就是可以将游戏处理成小二维数组（块）在一个大的二维数组（背景）中的运动，进行计算处理后，将结果用界面（如各种控件或图形）显示出来。也可以说是算法与界面独立，这样只用将界面中的图片改变，就可以形成不同的视觉效果，实现“扶肤”功能，而算法完全不用修改。
俄罗斯方块VB源代码：http://download.csdn.net/source/1738728 --------------------编程问答-------------------- 楼主简单的用and或or判断都是不对滴。
你要按照不同的方块分情况判断。

补充：VB ,  VBA