二十一点游戏是玩家要取得比庄家更大的点数总和，但点数超过二十一点即为爆牌，并输掉注码。J、Q、K算10点，A可算1点或11点，其余按牌面值计点数。“BlackJack”是由一张A和J、Q、K或10所组成。开始时每人发两张牌，一张明，一张暗，凡点数不足二十一点，可选择博牌。如果首两张牌是对子可选择分牌。

为简化起见，程序中只有两个玩家Dealer和Player，都发明牌，无下注过程，不记录输赢，不支持分牌和加倍等。二十一点游戏中，一张牌只要有四个属性说明：Face牌面大小、Suit牌面花色，Count点数，FaceUp牌面是否向上。因此，这里我们不用Card 类而用Card结构。

Structure card

Public face As Integer

Public suit As Integer

Public count As Integer

Public faceup As Boolean

End Structure

游戏开始时，我们首先要取一副牌，然后将牌洗好，指定从第几张牌开始发起。洗牌时为取得真正的随机数，用My.Computer.Clock.TickCount作产生随机数的种子。

Dim Deck() As card

Deck = New card(51) {}

Dim TopCard As Integer

Private Sub GetDeck()

Dim i, j As Integer

For i = 0 To 3

For j = 0 To 12

Deck(j + 13 * i).face = j

Deck(j + 13 * i).suit = i

If j < 10 Then

Deck(j + 13 * i).count = j + 1

Else

Deck(j + 13 * i).count = 10

End If

Deck(j + 13 * i).faceup = False

Next

Next

End Sub

Private Sub Shuffle()

Dim i, j, k As Integer

Dim tc As card

For k = 1 To 500

i = CType(My.Computer.Clock.TickCount * Rnd(), Integer) Mod 52

j = CType(Int(Rnd() * 52), Integer)

tc = Deck(i)

Deck(i) = Deck(j)

Deck(j) = tc

Next

topcard = 0

End Sub

游戏界面中，我们设置三个命令按钮，两个标签。Button1为“发牌”、Button2为“要牌”、Button3为“停牌”。Label1记录庄家点数，Label2记录玩家点数。游戏过程中，如果一副牌发完，立即重洗一副牌，并弹出消息对话框告知。以下列出三个按钮单击事件代码。其中庄家游戏过程中，为简化起见，未曾使用游戏技巧。

Dim playerCount As Integer = 0

Dim playerAce As Integer = 0

Dim dealerCount As Integer = 0

Dim dealerAce As Integer = 0

Dim ipcard, idcard As Integer

Private Sub delay(ByVal dt As Integer)

Dim t As Integer

t = My.Computer.Clock.TickCount

Do

If My.Computer.Clock.TickCount >= t + dt Then Exit Do

Loop

End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Button1.Visible = False

Label1.Text=””

Label2.Text=””

Label1.Refresh()

Label2.Refresh()

MyBase.CreateGraphics.Clear(Color.DarkGreen)

dealerAce = 0

playerAce = 0

dealerCount = 0

playerCount = 0

cdtDrawExt(MyBase.CreateGraphics.GetHdc, 200, 200, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)

playerCount += Deck(TopCard).count

If Deck(TopCard).face = 0 Then playerCount += 10 : playerAce += 1

TopCard += 1

If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")

Label2.Text = playerCount.ToString

Label2.Refresh()

delay(1000)

cdtDrawExt(MyBase.CreateGraphics.GetHdc, 200, 10, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)

dealerCount += Deck(TopCard).count

If Deck(TopCard).face = 0 Then dealerCount += 10 : dealerAce += 1

TopCard += 1

If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")

Label1.Text = dealerCount.ToString

Label1.Refresh()

delay(1000)

cdtDrawExt(MyBase.CreateGraphics.GetHdc, 220, 200, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)

playerCount += Deck(TopCard).count

If Deck(TopCard).face = 0 And playerAce = 0 Then playerCount += 10 : playerAce += 1

TopCard += 1

If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")

Label2.Text = playerCount.ToString

Label2.Refresh()

delay(1000)

cdtDrawExt(MyBase.CreateGraphics.GetHdc, 220, 10, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)

dealerCount += Deck(TopCard).count

If Deck(TopCard).face = 0 And dealerAce = 0 Then dealerCount += 10 : dealerAce += 1

TopCard += 1

If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")

Label1.Text = dealerCount.ToString

Label1.Refresh()

delay(1000)

ipcard = 2

idcard = 2

Button2.Visible = True

Button3.Visible = True

End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click

cdtDrawExt(MyBase.CreateGraphics.GetHdc, 200 + 20 * ipcard, 200, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)

playerCount += Deck(TopCard).count

If Deck(TopCard).face = 0 Then playerCount += 10 : playerAce += 1

TopCard += 1

If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")

ipcard += 1

Label2.Text = playerCount.ToString

Label2.Refresh()

If playerCount > 21 Then

If playerAce >= 1 Then

playerCount -= 10

playerAce -= 1

Label2.Text = playerCount.ToString

Label2.Refresh()

Else

MsgBox("Player loss!")

Button1.Visible = True

Button2.Visible = False

Button3.Visible = False

End If

End If

End Sub

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click

Button2.Visible = False

Button3.Visible = False

dealerPlay()

End Sub

Private Sub dealerPlay()

Do

If dealerCount < 17 Then

cdtDrawExt(MyBase.CreateGraphics.GetHdc, 200 + 20 * idcard, 10, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)

dealerCount += Deck(TopCard).count

If dealerCount > 21 And dealerAce = 1 Then dealerCount -= 10 : dealerAce -= 1

If Deck(TopCard).face = 0 And dealerCount <= 11 Then dealerCount += 10

TopCard += 1

If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")

idcard += 1

Else

Exit Do

End If

Loop

Label1.Text = dealerCount.ToString

Label1.Refresh()

If dealerCount <= 21 Then

If playerCount > dealerCount Then

MsgBox("Player win!")

Else

MsgBox("Dealer win!")

End If

Else

MsgBox("Player win!")

End If

Button1.Visible = True

Button2.Visible = False

Button3.Visible = False

End Sub

运行结果如下图所示：

三、 实践与提高

上述编程中,我们用了结构描述Card，对Card的Face取值（A，2，…，K）和Suit取值（Club，Diamond，Heart，Spade）用了数值0-12和0-3表示。游戏规则也作了简化，只有两个玩家，也未对玩家属性（如：财富、下注、所持牌、持牌点数等）进行描述。实践表明，较好的方法是用Card、player类，Face和Suit用枚举型数据。这些，我们可以在编程中逐步地添加完善。

随着编程实践的深入，我们的经验也会随之丰富起来。如何写一系列的类去支持各式游戏（包括升级、斗地主等需要用大小王牌的游戏）？如何记录玩家得分？如何支持网络？如何处理网络游戏中玩家离开？如此等等。经一个月、两个月，一年、两年的实践后，你将成为行家里手。