Snake in Small Basic

[Ed Price]

First published on MSDN on Dec 07, 2008

Authored by Vijaye Raji

This week's featured sample is the arcade classic Snake!  And it comes from PlayDeez , who has also written other interesting Small Basic games (check out the Small Basic forums for more such hotness.)

Here's the screenshot, followed by the source listing.

Initialize()
While (GameState <> "")
DoGameLoop()
EndWhile
Program.End()

Sub Initialize
InitializeVariables()
InitializeScreen()
EndSub

Sub InitializeVariables
Array.SetValue("DeltaX","North",0)
Array.SetValue("DeltaX","East",1)
Array.SetValue("DeltaX","South",0)
Array.SetValue("DeltaX","West",-1)
Array.SetValue("DeltaY","North",-1)
Array.SetValue("DeltaY","East",0)
Array.SetValue("DeltaY","South",1)
Array.SetValue("DeltaY","West",0)
Array.SetValue("NorthFlag","North",1)
Array.SetValue("NorthFlag","East",0)
Array.SetValue("NorthFlag","South",0)
Array.SetValue("NorthFlag","West",0)
Array.SetValue("SouthFlag","North",0)
Array.SetValue("SouthFlag","East",0)
Array.SetValue("SouthFlag","South",1)
Array.SetValue("SouthFlag","West",0)
Array.SetValue("EastFlag","North",0)
Array.SetValue("EastFlag","East",1)
Array.SetValue("EastFlag","South",0)
Array.SetValue("EastFlag","West",0)
Array.SetValue("WestFlag","North",0)
Array.SetValue("WestFlag","East",0)
Array.SetValue("WestFlag","South",0)
Array.SetValue("WestFlag","West",1)
Array.SetValue("DirectionInput","N","North")
Array.SetValue("DirectionInput","E","East")
Array.SetValue("DirectionInput","S","South")
Array.SetValue("DirectionInput","W","West")
GameDelay = 100
Score = 0
HighScore = 0
GameState = "TitleScreen"
ScreenDirty = 1
CurrentDirectory = Text.GetSubText(File.GetSettingsFilePath(),0,Text.GetLength(File.GetSettingsFilePath())-26)
EndSub

Sub InitializeScreen
GraphicsWindow.Show()
GraphicsWindow.Width = 640
GraphicsWindow.Height = 480
'TODO: remove hack when able to do so
GraphicsWindow.Width = 640
GraphicsWindow.KeyDown = HandleKeyPress
EndSub

Sub HandleTitleScreenKeyPress
Key = GraphicsWindow.LastKey
If (Key = "Escape") Then
GameState=""
Else
If (Key="F2") Then
GameState = "Play"
ScreenDirty = 1
Else
If (Key="F1") Then
GameState = "Instructions"
ScreenDirty = 1
DoInstructionLoop()
EndIf
EndIf
EndIf
EndSub

Sub HandleInstructionsKeyPress
Key = GraphicsWindow.LastKey
If (Key = "Escape") Then
GameState = "TitleScreen"
ScreenDirty = 1
DoTitleScreenLoop()
EndIf
EndSub

Sub HandlePlayKeyPress
Key = GraphicsWindow.LastKey
If (Key = "Left") Then
DirectionInput = DirectionInput + "W"
Else
If (Key = "Right") Then
DirectionInput = DirectionInput + "E"
Else
If (Key = "Up") Then
DirectionInput = DirectionInput + "N"
Else
If (Key = "Down") Then
DirectionInput = DirectionInput + "S"
EndIf
EndIf
EndIf
EndIf
EndSub

Sub HandleGameOverKeyPress
Key = GraphicsWindow.LastKey
If (Key = "Escape") Then
GameState=""
Else
If (Key="F2") Then
GameState = "Play"
ScreenDirty = 1
DoPlayLoop()
Else
If (Key="F1") Then
GameState = "Instructions"
ScreenDirty = 1
DoInstructionLoop()
EndIf
EndIf
EndIf
EndSub

Sub HandleKeyPress
If (GameState="TitleScreen") Then
HandleTitleScreenKeyPress()
Else
If (GameState="Instructions") Then
HandleInstructionsKeyPress()
Else
If (GameState="Play") Then
HandlePlayKeyPress()
Else
If (GameState="GameOver") Then
HandleGameOverKeyPress()
Else
EndIf
EndIf
EndIf
EndIf
EndSub

Sub DoTitleScreenLoop
If (ScreenDirty = 1) Then
ScreenDirty = 0
GraphicsWindow.Clear()
GraphicsWindow.BrushColor = "#000000"
GraphicsWindow.FontSize = 32
GraphicsWindow.DrawText(0,0,"SBSnake!")
GraphicsWindow.FontSize = 16
GraphicsWindow.DrawText(0,64," for instructions")
GraphicsWindow.DrawText(0,80," for a new game")
GraphicsWindow.DrawText(0,96," to exit")
EndIf
EndSub

Sub DoInstructionLoop
If (ScreenDirty = 1) Then
ScreenDirty = 0
GraphicsWindow.Clear()
GraphicsWindow.BrushColor = "#000000"
GraphicsWindow.FontSize = 32
GraphicsWindow.DrawText(0,0,"How To Play SBSnake!")
GraphicsWindow.FontSize = 16
GraphicsWindow.DrawText(0,64,"Use arrow keyss to move the snake")
GraphicsWindow.DrawText(0,80,"Avoid hitting your own tail")
GraphicsWindow.DrawText(0,96,"Avoid hitting the wall")
GraphicsWindow.DrawText(0,112,"Collect red pellets to accumulate score")
GraphicsWindow.DrawText(0,128," to return to main menu")
EndIf
EndSub

Sub AddPellet
PickPellet:
PelletX = Math.GetRandomNumber(40)
PelletY = Math.GetRandomNumber(30)
Color = GraphicsWindow.GetPixel(PelletX * 16 + 8, PelletY * 16 + 8)
If (Color = "#00FF00" Or Color="#FF0000") Then
Goto PickPellet
EndIf
GraphicsWindow.PenWidth = 0
GraphicsWindow.BrushColor = "#FF0000"
GraphicsWindow.FillRectangle(PelletX* 16+3, PelletY * 16+3,10,10)
EndSub

Sub DrawHead
GraphicsWindow.PenWidth = 0
GraphicsWindow.BrushColor = "#00FF00"
GraphicsWindow.FillRectangle(SnakeHeadX * 16+2, SnakeHeadY * 16+2,12,12)
If (Direction="South") Then
GraphicsWindow.FillRectangle(SnakeHeadX * 16+4, SnakeHeadY*16,8,4)
EndIf
If (Direction="North") Then
GraphicsWindow.FillRectangle(SnakeHeadX * 16+4, SnakeHeadY*16+12,8,4)
EndIf
If (Direction="East") Then
GraphicsWindow.FillRectangle(SnakeHeadX * 16, SnakeHeadY*16+4,4,8)
EndIf
If (Direction="West") Then
GraphicsWindow.FillRectangle(SnakeHeadX * 16+12, SnakeHeadY*16+4,4,8)
EndIf
EndSub

Sub EraseHead
If (GraphicsWindow.GetPixel(SnakeHeadX*16+8,SnakeHeadY*16)="#00FF00") Then
NorthFlag = 1
Else
NorthFlag = Array.GetValue("NorthFlag",Direction)
EndIf
If (GraphicsWindow.GetPixel(SnakeHeadX*16+8,SnakeHeadY*16+15)="#00FF00") Then
SouthFlag = 1
Else
SouthFlag = Array.GetValue("SouthFlag",Direction)
EndIf
If (GraphicsWindow.GetPixel(SnakeHeadX*16,SnakeHeadY*16+8)="#00FF00") Then
WestFlag = 1
Else
WestFlag = Array.GetValue("WestFlag",Direction)
EndIf
If (GraphicsWindow.GetPixel(SnakeHeadX*16+15,SnakeHeadY*16+8)="#00FF00") Then
EastFlag = 1
Else
EastFlag = Array.GetValue("EastFlag",Direction)
EndIf
GraphicsWindow.BrushColor = "#FFFFFF"
GraphicsWindow.FillRectangle(SnakeHeadX * 16, SnakeHeadY*16,16,16)
GraphicsWindow.BrushColor = "#00FF00"
If (AtePellet = 1) Then
GraphicsWindow.FillRectangle(SnakeHeadX * 16+3, SnakeHeadY*16+3,10,10)
Else
GraphicsWindow.FillRectangle(SnakeHeadX * 16+4, SnakeHeadY*16+4,8,8)
EndIf
If (NorthFlag = 1) Then
GraphicsWindow.FillRectangle(SnakeHeadX * 16+4, SnakeHeadY*16,8,4)
EndIf
If (SouthFlag = 1) Then
GraphicsWindow.FillRectangle(SnakeHeadX * 16+4, SnakeHeadY*16+12,8,4)
EndIf
If (WestFlag = 1) Then
GraphicsWindow.FillRectangle(SnakeHeadX * 16, SnakeHeadY*16+4,4,8)
EndIf
If (EastFlag = 1) Then
GraphicsWindow.FillRectangle(SnakeHeadX * 16+12, SnakeHeadY*16+4,4,8)
EndIf
EndSub

Sub EraseTail
If (GraphicsWindow.GetPixel(SnakeTailX*16+8,SnakeTailY*16)="#00FF00") Then
NorthFlag = 1
Else
NorthFlag = 0
EndIf
If (GraphicsWindow.GetPixel(SnakeTailX*16+8,SnakeTailY*16+15)="#00FF00") Then
SouthFlag = 1
Else
SouthFlag = 0
EndIf
If (GraphicsWindow.GetPixel(SnakeTailX*16,SnakeTailY*16+8)="#00FF00") Then
WestFlag = 1
Else
WestFlag = 0
EndIf
If (GraphicsWindow.GetPixel(SnakeTailX*16+15,SnakeTailY*16+8)="#00FF00") Then
EastFlag = 1
Else
EastFlag = 0
EndIf
GraphicsWindow.BrushColor = "#FFFFFF"
GraphicsWindow.FillRectangle(SnakeTailX * 16, SnakeTailY*16,16,16)

If (NorthFlag = 1) Then
TailDirection = "North"
EndIf
If (SouthFlag = 1) Then
TailDirection = "South"
EndIf
If (EastFlag = 1) Then
TailDirection = "East"
EndIf
If (WestFlag = 1) Then
TailDirection = "West"
EndIf
SnakeTailX = SnakeTailX + Array.GetValue("DeltaX",TailDirection)
SnakeTailY = SnakeTailY + Array.GetValue("DeltaY",TailDirection)
If (GraphicsWindow.GetPixel(SnakeTailX*16+3,SnakeTail*16+3)="#00FF00") Then
TailPellet = 1
Else
TailPellet = 0
EndIf
If (GraphicsWindow.GetPixel(SnakeTailX*16+8,SnakeTailY*16)="#00FF00") Then
NorthFlag = 1
Else
NorthFlag = 0
EndIf
If (GraphicsWindow.GetPixel(SnakeTailX*16+8,SnakeTailY*16+15)="#00FF00") Then
SouthFlag = 1
Else
SouthFlag = 0
EndIf
If (GraphicsWindow.GetPixel(SnakeTailX*16,SnakeTailY*16+8)="#00FF00") Then
WestFlag = 1
Else
WestFlag = 0
EndIf
If (GraphicsWindow.GetPixel(SnakeTailX*16+15,SnakeTailY*16+8)="#00FF00") Then
EastFlag = 1
Else
EastFlag = 0
EndIf
If (TailDirection="North") Then
SouthFlag = 0
EndIf
If (TailDirection="South") Then
NorthFlag = 0
EndIf
If (TailDirection="East") Then
WestFlag = 0
EndIf
If (TailDirection="West") Then
EastFlag = 0
EndIf
GraphicsWindow.FillRectangle(SnakeTailX * 16, SnakeTailY*16,16,16)
GraphicsWindow.BrushColor = "#00FF00"
If (TailPellet = 1) Then
GraphicsWindow.FillRectangle(SnakeTailX * 16+3, SnakeTailY*16+3,10,10)
Else
GraphicsWindow.FillRectangle(SnakeTailX * 16+4, SnakeTailY*16+4,8,8)
EndIf
If (NorthFlag = 1) Then
GraphicsWindow.FillRectangle(SnakeTailX * 16+4, SnakeTailY*16,8,4)
EndIf
If (SouthFlag = 1) Then
GraphicsWindow.FillRectangle(SnakeTailX * 16+4, SnakeTailY*16+12,8,4)
EndIf
If (WestFlag = 1) Then
GraphicsWindow.FillRectangle(SnakeTailX * 16, SnakeTailY*16+4,4,8)
EndIf
If (EastFlag = 1) Then
GraphicsWindow.FillRectangle(SnakeTailX * 16+12, SnakeTailY*16+4,4,8)
EndIf
EndSub

Sub ProcessDirectionInput
If (Text.GetLength(DirectionInput)>0) Then
Temp = Text.GetSubText(DirectionInput,0,1)
DirectionInput = Text.GetSubText(DirectionInput,1,Text.GetLength(DirectionInput)-1)
Direction = Array.GetValue("DirectionInput",Temp)
EndIf
EndSub

Sub StartGame
Direction=""
DirectionInput=""
SnakeLength = 1
SnakeMaximumLength = 4
SnakeHeadX = 20
SnakeHeadY = 15
SnakeTailX = 20
SnakeTailY = 15
AtePellet = 0
Score = 0
GraphicsWindow.Clear()
DrawHead()
AddPellet()
UpdateScore()
EndSub

Sub UpdateScore
GraphicsWindow.Title = "SBSnake - "+Score
EndSub

Sub DoPlayLoop
If (ScreenDirty = 1) Then
ScreenDirty = 0
StartGame()
Else
If (Direction <> "" Or DirectionInput<>"") Then
ProcessDirectionInput()
EraseHead()
SnakeHeadX = SnakeHeadX + Array.GetValue("DeltaX",Direction)
SnakeHeadY = SnakeHeadY + Array.GetValue("DeltaY",Direction)
If (SnakeHeadX<0 Or SnakeHeadX>39 Or SnakeHeadY < 0 Or SnakeHeadY > 29) Then
GameState = "GameOver"
ScreenDirty = 1
Else
If (GraphicsWindow.GetPixel(SnakeHeadX*16+8,SnakeHeadY*16+8)="#FF0000") Then
Score = Score + 1
UpdateScore()
AtePellet = 1
SnakeMaximumLength = SnakeMaximumLength + 2
AddPellet()
Else
AtePellet = 0
EndIf
If (GraphicsWindow.GetPixel(SnakeHeadX*16+8,SnakeHeadY*16+8)="#00FF00") Then
GameState = "GameOver"
DrawHead()
ScreenDirty = 1
Else
SnakeLength = SnakeLength + 1
DrawHead()
While (SnakeLength>SnakeMaximumLength)
EraseTail()
SnakeLength = SnakeLength - 1
EndWhile
Program.Delay(GameDelay)
EndIf
EndIf
EndIf
EndIf
EndSub

Sub DoGameOverLoop
If (ScreenDirty = 1) Then
ScreenDirty = 0
GraphicsWindow.BrushColor = "#000000"
GraphicsWindow.FontSize = 32
GraphicsWindow.DrawText(0,0,"Game Over!")
GraphicsWindow.FontSize = 16
GraphicsWindow.DrawText(0,64," for instructions")
GraphicsWindow.DrawText(0,80," for a new game")
GraphicsWindow.DrawText(0,96," to exit")
EndIf
EndSub

Sub DoGameLoop
If (GameState = "TitleScreen") Then
DoTitleScreenLoop()
Else
If (GameState = "Instructions") Then
DoInstructionLoop()
Else
If (GameState = "Play") Then
DoPlayLoop()
Else
If (GameState = "GameOver") Then
DoGameOverLoop()
EndIf
EndIf
EndIf
EndIf
EndSub

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