Nibbles
In this part of the Mono Winforms programming tutorial, we will create a Nibbles game clone.
Nibbles game
Nibbles is an older classic video game. It was first created in late 70s. Later it was brought to PCs. In this game the player controls a worm. The objective is to eat as many apples as possible. Each time the worm eats an apple, its body grows. It must avoid the walls and its own body.
Development
The size of each of the joints of a worm is 10px. The worm is controlled with the cursor keys. Initially the worm has three joints. The game is started by pressing one of the cursor keys. If the game is finished, we display Game Over message in the middle of the Board.
Imports System
Imports System.Collections
Imports System.ComponentModel
Imports System.Drawing
Imports System.Data
Imports System.Windows.Forms
NameSpace BoardSpace
public class Board
Inherits UserControl
Const WIDTH As Integer = 300
Const HEIGHT As Integer = 300
Const DOT_SIZE As Integer = 10
Const ALL_DOTS As Integer = 900
Const RAND_POS As Integer = 27
Const DELAY As Integer = 140
Dim x(ALL_DOTS) As Integer
Dim y(ALL_DOTS) As Integer
Dim dots As Integer
Dim apple_x As Integer
Dim apple_y As Integer
Dim left As Boolean = False
Dim right As Boolean = True
Dim up As Boolean = False
Dim down As Boolean = False
Dim inGame As Boolean = True
Private Dim timer As Timer
Private Dim dot As Bitmap
Private Dim apple As Bitmap
Private Dim head As Bitmap
Private Dim components As IContainer
Public Dim BORDER_WIDTH As Integer
Public Dim TITLEBAR_HEIGHT As Integer
Public Sub New
components = New Container
Me.BackColor = Color.Black
Me.DoubleBuffered = True
Me.ClientSize = New Size(WIDTH, HEIGHT)
Try
dot = New Bitmap("dot.png")
apple = New Bitmap("apple.png")
head = New Bitmap("head.png")
Catch e As Exception
Console.WriteLine(e.Message)
Environment.Exit(1)
End Try
Me.InitGame
End Sub
Private Sub InitGame
dots = 3
For z As Integer = 0 To dots-1
x(z) = 50 - z*10
y(z) = 50
Next
Me.LocateApple
AddHandler Me.KeyUp, AddressOf Me.OnKeyUp
timer = New Timer(Me.components)
timer.Enabled = True
timer.Interval = DELAY
AddHandler timer.Tick, AddressOf Me.OnTick
AddHandler Me.Paint, AddressOf Me.OnPaint
End Sub
Private Sub OnPaint(ByVal sender As Object, _
ByVal e As PaintEventArgs)
Dim g As Graphics = e.Graphics
If inGame
Me.DrawObjects(g)
Else
Me.GameOver(g)
End If
End Sub
Private Sub DrawObjects(ByVal g As Graphics)
g.DrawImage(apple, apple_x, apple_y)
For z As Integer = 0 To dots-1
If z = 0
g.DrawImage(head, x(z), y(z))
Else
g.DrawImage(dot, x(z), y(z))
End If
Next
End Sub
Private Sub GameOver(ByVal g As Graphics)
Dim msg As String = "Game Over"
Dim rectF As RectangleF = RectangleF.op_Implicit(Me.ClientRectangle)
Dim format As New StringFormat
format.Alignment = StringAlignment.Center
format.LineAlignment = StringAlignment.Center
g.DrawString(msg, Font, Brushes.White, rectF , format)
timer.Stop
End Sub
Private Sub CheckApple
If x(0) = apple_x And y(0) = apple_y
dots += 1
Me.LocateApple
End If
End Sub
Private Sub Move
For z As Integer = dots To 1 Step -1
x(z) = x(z - 1)
y(z) = y(z - 1)
Next
If left
x(0) -= DOT_SIZE
End If
If right
x(0) += DOT_SIZE
End If
If up
y(0) -= DOT_SIZE
End If
If down
y(0) += DOT_SIZE
End If
End Sub
Private Sub CheckCollision
For z As Integer = dots To 1 Step -1
If z > 4 And x(0) = x(z) And y(0) = y(z)
inGame = False
End If
Next
If y(0) >= HEIGHT - DOT_SIZE - TITLEBAR_HEIGHT
inGame = False
End If
If y(0) < 0
inGame = False
End If
If x(0) >= WIDTH - DOT_SIZE - BORDER_WIDTH:
inGame = False
End If
If x(0) < 0
inGame = False
End If
End Sub
Private Sub LocateApple
Dim rand As New Random
Dim r As Integer = rand.Next(RAND_POS)
apple_x = r * DOT_SIZE
r = rand.Next(RAND_POS)
apple_y = r * DOT_SIZE
End Sub
Private Sub OnTick(ByVal sender As Object, ByVal e As EventArgs)
If inGame
Me.CheckApple
Me.CheckCollision
Me.Move
End If
Me.Refresh
End Sub
Private Sub OnKeyUp(ByVal sender As Object, ByVal e As KeyEventArgs)
Dim key As Integer = e.KeyCode
If key = Keys.Left And Not right
left = True
up = False
down = False
End If
If key = Keys.Right And Not left
right = True
up = False
down = False
End If
If key = Keys.Up And Not down
up = True
right = False
left = False
End if
If key = Keys.Down And Not up
down = True
right = False
left = False
End If
End Sub
End Class
End Namespace
First we will define the constants used in our game.
The WIDTH and HEIGHT constants determine the size of the Board. The DOT_SIZE is the size of the apple and the dot of the worm. The ALL_DOTS constant defines the maximum number of possible dots on the Board. (900 = 300*300/10*10) The RAND_POS constant is used to calculate a random position of an apple. The DELAY constant determines the speed of the game.
Dim x(ALL_DOTS) As Integer Dim y(ALL_DOTS) As Integer
These two arrays store x, y coordinates of all joints of a worm.
In the Move method we have the key algorithm of the game. To understand it, look at how the worm is moving. You control the head of the worm. You can change its direction with the cursor keys. The rest of the joints move one position up the chain. The second joint moves where the first was, the third joint where the second was etc.
For z As Integer = dots To 1 Step -1
x(z) = x(z - 1)
y(z) = y(z - 1)
Next
This code moves the joints up the chain.
If left
x(0) -= DOT_SIZE
End If
Move the head to the left.
In the CheckCollision method, we determine if the worm has hit itself or one of the walls.
For z As Integer = dots To 1 Step -1
If z > 4 And x(0) = x(z) And y(0) = y(z)
inGame = False
End If
Next
Finish the game, if the worm hits one of its joints with the head.
If y(0) >= HEIGHT - DOT_SIZE - TITLEBAR_HEIGHT
inGame = False
End If
Finish the game, if the worm hits the bottom of the Board.
The followintg image helps understand the collision of the worm object with the bottom of the board.
The locateApple method locates an apple randomly on the form.
Dim rand As New Random Dim r As Integer = rand.Next(RAND_POS)
We get a random number from 0 to RAND_POS - 1.
apple_x = r * DOT_SIZE ... apple_y = r * DOT_SIZE
These line set the x, y coordinates of the apple object.
In the OnKeyUp method, we deternime which keys the player hit.
If key = Keys.Left And Not right
left = True
up = False
down = False
End If
If we hit the left cursor key, we set left variable to True. This variable is used in the Move method to change coordinates of the worm object. Notice also, that when the worm is heading to the right, we cannot turn immediately to the left.
' ZetCode Mono Visual Basic Winforms tutorial
'
' In this program, we create
' a Nibbles game clone
'
' author jan bodnar
' last modified May 2009
' website www.zetcode.com
Imports System
Imports System.Drawing
Imports System.Windows.Forms
Public Class WinVBApp
Inherits Form
Public Sub New
Me.Text = "Nibbles"
Me.FormBorderStyle = FormBorderStyle.FixedSingle
Dim borderWidth As Integer = (Me.Width - Me.ClientSize.Width) / 2
Dim titleBarHeight As Integer = Me.Height - Me.ClientSize.Height - borderWidth
Dim board As New BoardSpace.Board
board.BORDER_WIDTH = borderWidth
board.TITLEBAR_HEIGHT = titleBarHeight
Me.Controls.Add(board)
Me.CenterToScreen
End Sub
Public Shared Sub Main
Application.Run(New WinVBApp)
End Sub
End Class
This is the main class.
This was the Nibbles game programmed using the Mono Winforms library and the Visual Basic language.