VB小游戏“让子弹飞”【vb吧】

主要游戏内容就是控制飞机移动、发射子弹，子弹碰到石子会将其击碎。
为此，我定义了以下几个类 Plane，Bullet，Stone，Position。

其中Position类与自定义类型的功能是一样的。只不过**中使用自定义类型会出现一些问题。
此游戏没有提供很好的用户体验，只是作为一种游戏编程的尝试（PS：第一次写游戏，不知道思路对不对，欢迎高手批评指教

），不过只要稍微充实一下代码即可获得不错的改善。
美观方面：只需重写Plane，Bullet，Stone这三个类的Paint方法即可获得漂亮的界面。
控制方面：用Timer去检测按键应该可以使操作更加灵敏。
（全部使用VB内置功能，没有直接调用API，比较容易理解）

下载地址：http://itianda.googlecode.com/files/BulletFly.rar

'以下在Form1
Option Explicit
Dim colObj As New Collection
Dim timStart As Date
Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
Select Case UCase(Chr(KeyCode))
     Case "A"
         colObj(1).Left = colObj(1).Left - 1
     Case "D"
         colObj(1).Left = colObj(1).Left + 1
     Case "W"
         colObj(1).Top = colObj(1).Top - 1
     Case "S"
         colObj(1).Top = colObj(1).Top + 1
     Case Else
         If KeyCode = vbKeySpace Then AddObject New Bullet, colObj(1).Left, colObj(1).Top
     End Select
End Sub
Private Sub Form_Load()
Me.Caption = "让子弹飞!"
Me.KeyPreview = True
Me.ScaleMode = vbPixels
Me.Width = 220 * 15
Me.Height = 300 * 15
GenerateObjects
timStart = Now
MsgBox "A,S,D,W 键控制方向，Space 键发射子弹" & vbNewLine & "itianda 温馨提示：请不要碰到石子哦！"
Timer1.Enabled = True
End Sub
Private Sub GenerateObjects()
AddObject New Plane, 100, 150
Dim i As Long
For i = 0 To 8
     AddObject New Stone, i * 20 + 20, 30
Next
End Sub
Private Sub AddObject(pObj, pLeft As Long, pTop As Long)
Set pObj.Parent = Me
pObj.Left = pLeft
pObj.Top = pTop
colObj.Add pObj
End Sub
Private Sub Form_Paint()
Dim count As Long
count = colObj.count
Dim i As Long
For i = 1 To count
     colObj(i).Paint
Next
End Sub
Private Sub Timer1_Timer()
Dim colBullet As New Collection
Dim colStone As New Collection
Dim count As Long
count = colObj.count
Dim i As Long
For i = 1 To count
     With colObj(i)
         Dim pos As Position
         Set pos = New Position
         pos.Index = i
         pos.X = .Left
         pos.Y = .Top
         Select Case .Class
         Case "Bullet"
             colBullet.Add pos
         Case "Stone"
             colStone.Add pos
         End Select
     End With
Next
Dim bulletCount, stoneCount As Long
bulletCount = colBullet.count
stoneCount = colStone.count
If stoneCount = 0 Then
     Timer1.Enabled = False
     MsgBox "您胜利了!用时 " & CDate(Now - timStart)

     End
End If
Dim j As Long
For j = 1 To stoneCount
     If colObj(1).Left >= colStone(j).X - 5 And colObj(1).Left <= colStone(j).X + 5 And colObj(1).Top >= colStone(j).Y - 10 And colObj(1).Top <= colStone(j).Y + 10 Then
         Timer1.Enabled = False
         MsgBox "您失败了!"
         End
     End If
Next
Dim colObjDel As New Collection
Dim colObjNew As New Collection
For i = 1 To bulletCount
     For j = 1 To stoneCount
         If colBullet(i).X >= colStone(j).X - 4 And colBullet(i).X <= colStone(j).X + 4 And colBullet(i).Y >= colStone(j).Y - 4 And colBullet(i).Y <= colStone(j).Y + 4 Then
             Caption = TimeValue(Now) & ":消除一枚石子"
             colObjDel.Add colStone(j).Index
         End If
     Next
Next
count = colBullet.count
For i = 1 To count
     If colBullet(i).Y < 0 Then colObjDel.Add colBullet(i).Index
Next
count = colStone.count
For i = 1 To count
     If colStone(i).X < 5 Then colObj(colStone(i).Index).Left = 200
     If colStone(i).X > 195 Then colObj(colStone(i).Index).Left = 5
    colObj(colStone(i).Index).Top = colStone(i).Y Mod 200 + 2
Next
count = colObjDel.count
Sort colObjDel
For i = 1 To count
     colObj.Remove colObjDel(i)
Next
count = colObj.count
For i = 1 To count
     If colObj(i).Class = "Stone" Then
         colObj(i).Top = colObj(i).Top + Int(Rnd * 5) - 2
         colObj(i).Left = colObj(i).Left + Int(Rnd * 5) - 2
     End If
Next
count = colObj.count
For i = 1 To count
     If colObj(i).Class = "Bullet" Then
         colObj(i).Top = colObj(i).Top - 1
     End If
Next
Me.Refresh
End Sub
Private Sub Sort(ByRef pCollection As Collection)
Dim count
count = pCollection.count
Dim j, i
Dim arr() As Long
ReDim arr(count)
For i = 1 To count
     arr(i - 1) = pCollection(i)
Next
For j = 1 To count
     For i = 0 To count - 2
         If arr(i) < arr(i + 1) Then Swap arr(i), arr(i + 1)
     Next i
Next j
Dim colNew As New Collection
For i = 0 To count - 1
     colNew.Add arr(i)
Next
Set pCollection = colNew
End Sub
Private Sub Swap(ByRef a, ByRef b)
Dim c
c = a
a = b
b = c
End Sub