[RESOLVED] Help for a noob

[cicatrix]

We'll need a form, a picturebox, called picDisp and a button called btnStart (see pic):


First of all we'll need a game field and its contents:

Public Enum SquareContents
        Empty = 0
        Food = 1
        Obstacle = 2
        Body = 3
End Enum

Public Const FIELD_WIDTH As Integer = 30
Public Const FIELD_HEIGHT As Integer = 30
Public Shared GameField(0 To FIELD_WIDTH - 1, 0 To FIELD_HEIGHT - 1) As SquareContents

Public Enum Directions
        Left
        Right
        Up
        Down
End Enum

Now, let's create our snake:

Public Class Snake
        ' His body is simply a queue of points
        ' A queue works by the FIFO principle - First In - First Out
        Public BodyCells As New Queue(Of Point)
       
        ' The direction of his movement
        Public Direction As Directions
 
        ' The location of his head
        Public HeadLocation As Point
 
        ' We'll need two events
        Public Event PainfulDeath() ' Game over
        Public Event YumYum() ' Snake eats
 
Public Sub New()
            HeadLocation = New Point(FIELD_WIDTH \ 2, FIELD_HEIGHT \ 2) ' We place him in the center
            BodyCells.Enqueue(HeadLocation) ' We add his only cell to his body
            Direction = Directions.Right  ' ... and make him look to the right
End Sub
 
' Now, what will our snake do with each heatbeat?
   Public Sub Tick()
            Dim NextCell As Point = HeadLocation  ' Where is the next cell
            Select Case Direction 
                Case Directions.Up 
                    NextCell.Y -= 1  
                    If NextCell.Y < 0 Then
                        RaiseEvent PainfulDeath()  ' ... kill the poor beast.
                        Exit Sub
                    End If
                Case Directions.Down
                    NextCell.Y += 1
                    If NextCell.Y = FIELD_HEIGHT Then
                        RaiseEvent PainfulDeath()
                        Exit Sub
                    End If
                Case Directions.Left 
                    NextCell.X -= 1
                    If NextCell.X < 0 Then
                        RaiseEvent PainfulDeath()
                        Exit Sub
                    End If
                Case Directions.Right
                    NextCell.X += 1
                    If NextCell.X = FIELD_WIDTH Then
                        RaiseEvent PainfulDeath()
                        Exit Sub
                    End If
            End Select
 
            ' What do we have in this cell
            Select Case GameField(NextCell.X, NextCell.Y)             
                Case SquareContents.Body, SquareContents.Obstacle  ' bumped into an obstacle
                    RaiseEvent PainfulDeath()                                   
                    Exit Sub
                Case SquareContents.Food  '  some food here
                    BodyCells.Enqueue(NextCell) '  add another cell to body
                    HeadLocation = NextCell  
                    GameField(NextCell.X, NextCell.Y) = SquareContents.Body  ' Delete eaten food
                    RaiseEvent YumYum()     ' Gimme more food
 
                Case SquareContents.Empty  
                    BodyCells.Enqueue(NextCell) ' The tricky part - we add a body cell here..
                    HeadLocation = NextCell        
                    Dim Tail As Point = BodyCells.Dequeue()  '  ... and cut off his tail
                    GameField(Tail.X, Tail.Y) = SquareContents.Empty  
                    GameField(NextCell.X, NextCell.Y) = SquareContents.Body
            End Select
        End Sub
End Class

Something that would drive our game - a timer and some other helpers at the class level:

Public TICKS_FOR_FOOD As Integer   
                                                           
Public Bob As Snake ' Here's our Bob
Public CellSize As Size ' This is a size in pixels of one field cell (we'll determine it later)
Public tmr As Timer ' Main timer
Public FoodAt As Point ' Where the food is
Public KeepFood As Integer = 0 ' Ticks remaining before the food is spoiled
 
' Colors:
Public pGrass As Color
Public pFood As Color
Public pBody As Color
Public pObstacle As Color
 
Public GameOver As Boolean = False

A few preparations:

Private Sub frmSnake_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Me.KeyPreview = True
        tmr = New Timer
        tmr.Interval = 100 ' Setting timer interval (this value actually controls the speed of the game)
' the less it is the faster the game
        tmr.Enabled = False
 
' Colors:
        pGrass = Color.DarkGreen
        pFood = Color.Red
        pBody = Color.Yellow
        pObstacle = Color.White
 
        AddHandler tmr.Tick, AddressOf tmr_Tick   ' Making timer work
End Sub
 
' Update the size of the game field cell in pixels:
Private Sub frmSnake_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize
        CellSize.Width = CInt(picDisp.Width / FIELD_WIDTH)        
        CellSize.Height = CInt(picDisp.Height / FIELD_HEIGHT)
End Sub

Clicking the start button:

Private Sub btnStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.Click
        Bob = New Snake
        ReDim GameField(0 To FIELD_WIDTH - 1, 0 To FIELD_HEIGHT - 1) ' Clear the game field
        AddHandler Bob.PainfulDeath, AddressOf EndGame ' Show 'Game Over' if snake dies
        AddHandler Bob.YumYum, AddressOf PlaceNewFood ' For placing food
 
        tmr.Enabled = True
        btnStart.Enabled = False
        GameOver = False
End Sub
 
' Tell Bob where to go:
Private Sub frmSnake_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown
        Select Case e.KeyCode
            Case Keys.Left
                If Bob.Direction = Directions.Right Then Exit Sub
                Bob.Direction = Directions.Left
            Case Keys.Right
                If Bob.Direction = Directions.Left Then Exit Sub
                Bob.Direction = Directions.Right
            Case Keys.Up
                If Bob.Direction = Directions.Down Then Exit Sub
                Bob.Direction = Directions.Up
            Case Keys.Down
                If Bob.Direction = Directions.Up Then Exit Sub
                Bob.Direction = Directions.Down
        End Select
End Sub
 
' Bob dies:
Public Sub EndGame()
        GameOver = True
        tmr.Stop()
        btnStart.Enabled = True
        picDisp.Invalidate()
End Sub
 
' Game tick:
Public Sub tmr_Tick(ByVal sender As Object, ByVal e As EventArgs)
 
        If KeepFood = 0 Then 
              PlaceNewFood(EmptyCell:=True) ' We need to remove the old food and place a new one
              Dim rng As New Random
              TICKS_FOR_FOOD = rng.Next(10, 40) 
        End If
 
        KeepFood += 1  
        If KeepFood > TICKS_FOR_FOOD Then KeepFood = 0   ' Food is spolied if KeepFood = 0
        Bob.Tick()  ' Kick Bob to move
        picDisp.Invalidate()  ' Redraw screen
End Sub

Providing food is an important business:

Public Sub PlaceNewFood(Optional ByVal EmptyCell As Boolean = False)
        Dim rng As New Random
        Dim fx, fy As Integer
 
        Do     
            fx = rng.Next(0, FIELD_WIDTH)
            fy = rng.Next(0, FIELD_HEIGHT)
        Loop While GameField(fx, fy) <> SquareContents.Empty
 
        If EmptyCell Then   ' If we need to remove the old food we do that:
            GameField(FoodAt.X, FoodAt.Y) = SquareContents.Empty
        End If
 
        GameField(fx, fy) = SquareContents.Food       '  New food is placed
        FoodAt.X = fx   ' We should remember where it is to remove it later
        FoodAt.Y = fy
    End Sub
 
' Drawing the game screen:
Private Sub DrawGameField(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles picDisp.Paint
        
        If GameOver Then
            Dim fnt As New Font(Me.Font.FontFamily, 42, FontStyle.Bold, GraphicsUnit.Pixel)
            Dim txt As String = "GAME OVER"
            Dim TextSize As SizeF = e.Graphics.MeasureString(txt, fnt, New SizeF(picDisp.Width, fnt.Height))
            e.Graphics.DrawString(txt, fnt, Brushes.Red, _
                                  CSng(picDisp.Width / 2 - TextSize.Width / 2), _
                                  CSng(picDisp.Height / 2 - TextSize.Height / 2))
            Exit Sub
        End If
 
        Dim x, y As Integer
 
        ' Draw each game square them:
        For y = 0 To FIELD_HEIGHT - 1
            For x = 0 To FIELD_WIDTH - 1
                Dim cellRect As New Rectangle(x * CellSize.Width, y * CellSize.Height, CellSize.Width, CellSize.Height)
 
                Select Case GameField(x, y)
                    Case SquareContents.Empty
                        e.Graphics.FillRectangle(New SolidBrush(pGrass), cellRect)
                    Case SquareContents.Body
                        e.Graphics.FillRectangle(New SolidBrush(pGrass), cellRect)
                        e.Graphics.FillEllipse(New SolidBrush(pBody), cellRect)
                    Case SquareContents.Food
                        e.Graphics.FillRectangle(New SolidBrush(pGrass), cellRect)
                        e.Graphics.FillEllipse(New SolidBrush(pFood), cellRect)
                    Case SquareContents.Obstacle
                        e.Graphics.FillRectangle(New SolidBrush(pObstacle), cellRect)
                End Select
            Next
        Next
    End Sub

That's all. Complete source code is attached.