Challenge #16 - Snake Game

[kevin]

Challenge #16 - Snake Game

     This is an another retro game remake challenge.  Your objective is to make your own version of the classic Snake / Tron game.    In your edition of  game,  the player will guide the snakes head in four directions using the keys or joy pad.  The snake is constantly moving,  it should never stop.   It can not move over/through itself or screen edges (or other walls).   So if it's moving left,  the player would die if they try to move right. 

    The objective is to guide to snake (without touching it self or the walls) to pick up a food items.  You pick up items by running into them with the snakes head.  With each item the snake eats,  it grows one link longer.     Food items should appear randomly on the screen, for a random amount of time, before moving to another location.  So the player has to react quickly to collect them.  As an added bonus the player could have a health bar,  indicating how it's been since the player last ate.  if the bar runs out, the snake dies from starvation.

    While a very simple game on the surface,  it includes a number of good challenges for new game programmers.  Namely , getting your head around object management.  So you're going to have to build some code to cope with managing the various food items objects, the snakes growing length and the collisions between the snake and the food and snake and itself... 

     As with all challenges, the visuals/physics are not important, the challenge here is core game mechanic.  Good luck


Reference Materials

  Epic Snake



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[Big C.]

ok here is my mockup...

PlayBASIC Code: [Select]

; PROJECT : Snake-Challenge-Light
; AUTHOR  : Big C.
; CREATED : 03.03.2009
; EDITED  : 08.03.2009
; ---------------------------------------------------------------------

RemStart
Your task is to guide the snake so it eats the food.
The quicker you eat, the more you score.
And just like real food-eating snakes, the more you gobble,
the longer you become.  Try To steer clear of your own
growing tail (and avoid the walls in a future version)...
it won't be long before it's game over.

Features:

08.03.09 V0.02
-  If it's moving left, the player would die if they try to move right.
-  It can not move through screen edges.
-  Some minor changes 

06.03.09 V0.01
-  The player will guide the snakes head in four directions using the keys
-  The snake is constantly moving,  it should never stop.
-  It can not move over/through itself
-  Food items should appear randomly on the screen
-  Pick up items by running into them with the snakes head
-  With each item the snake eats,  it grows one link longer.

ToDo's:
-  It can not move through other ingame walls (in future version).
-  Food items should appear for a random amount of time, before moving to another location.
-  Bonus: The player could have a health bar,  indicating how it's been since the player last ate.
          If the bar runs out, the snake dies from starvation.

RemEnd

OpenScreen 640,480,16,1

TitleScreen "Challenge #16 - Snake Game coded with PB V1.64i - V0.02"

Constant North = 1
Constant East = 2
Constant South = 3
Constant West = 4

Global Direction = East

Global Head_X = 15   ;starting X-Point of our Snake-Head
Global Head_Y = 12   ;starting Y-Point of our Snake-Head
Global Food_X = RndRange(0, 63)
Global Food_Y = RndRange(0, 47)

Global Eat = 0
Global Score = 0
Global Size = 0
Global GameOver = 0

Global GetTime
Global LastMove = 0

; This Type define the position of body item
Type TSnake
   PosX
   PosY
EndType

;create a Linked List for the snakebody
Dim Snake As TSnake List

;our snake-body has 5 items
/*For I = 0 To 4
   Snake = New TSnake
   Snake.PosX = Head_X - 5 + I
   Snake.PosY = Head_Y
Next I*/

Psub CheckInput()
   ;check for North and not South
   If UpKey()
      If Direction <> South
         Direction = North
      Else
         GameOver = 1
      EndIf
   EndIf
   
   ;check for East and not West
   If RightKey()
      If Direction <> West
         Direction = East
      Else
         GameOver = 1
      EndIf
   EndIf
   
   ;check for South and not North
   If DownKey()
      If Direction <> North
         Direction = South
      Else
         GameOver = 1
      EndIf
   EndIf
   
   ;check for West and not East
   If LeftKey()
      If Direction <> East
         Direction = West
      Else
         GameOver = 1
      EndIf
   EndIf
EndPsub

Psub MoveSnake()
   GetTime = Timer()
   ;slow down the speed... after 75 millisec snake is moving
   If (GetTime - LastMove) > 75
      LastMove = GetTime
   
      ;check if snake has found something to eat
      If Head_X = Food_X And Head_Y = Food_Y
         Food_X = RndRange(0, 63)
         Food_Y = RndRange(0, 47)
         Eat = 1
         Score = Score + 10
      Else
         Eat = 0
      EndIf    
      
      ;here we let snake growing... Everytime snake head is moving
      ;to a new tile create a new type instance
      Snake = New TSnake
      Snake.PosX = Head_X
      Snake.PosY = Head_Y
      
      Head_X = Head_X - (Direction=West) + (Direction=East)
      Head_Y = Head_Y - (Direction=North) + (Direction=South)
      
      If Head_X < 0 Or Head_X > 64 Or Head_Y < 0 Or Head_Y > 48
         GameOver = 1
      EndIf

      /*If Head_X < 0 Then Head_X = 63
      If Head_X > 63 Then Head_X = 0
      If Head_Y < 0 Then Head_Y = 47
      If Head_Y > 47 Then Head_Y = 0*/


Login required to view complete source code

For better understanding what is happend if snake didn't find to eat and is moving his body here is my testcode to check the Linked List.

PlayBASIC Code: [Select]

; PROJECT : Project1
; AUTHOR  : Big C.
; CREATED : 06.03.2009
; EDITED  : 06.03.2009
; ---------------------------------------------------------------------

Type TTest
   Number
   Item$
EndType

Dim Test As TTest List

Global i = 0

Do
   Cls 0
   Print "Up Arrow Key: New Object"
   Print "Down Arrow Key: Delete First Item"
   
   If UpKey()
      i = i + 1
      Test = New TTest
      Test.Number = i
      Test.Item$ = "Item"+Str$(i)
      FlushKeys
   EndIf
   
   If DownKey()
      For Each Test()
         If GetListNext(Test()) = -1   
            First = GetListFirst(Test())
            Item = GetListPos(Test())
            Test = NULL
         EndIf
      Next
      FlushKeys
   EndIf
      
   Print "ListSize: " + Str$(GetListSize(Test())) + "   First: " + Str$(First) + "    Pos: " + Str$(Item)
      
   For Each Test()
       Print "Nr. " + Str$(Test.Number) + " Item: " + Test.Item$ + " Position: " + Str$(GetListPos(Test()))
   Next
   
   Sync
   
Loop

08.03.09 Updat to V0.02... two less ToDo's

Big C.

[micky4fun]

Hi Big C.

nice little demo , works very well , a 2 player version would be good i think , both players would have to race to pickup item while missing each other

thanks for posting code has help me a lot to understand the how segmant follows each other and more linked lists understanding

im going to give the challenge a go try and make a full game of it , but will post outcome if i get that far in the show case part of forum
as its not all my code , just modifyed snippets of playbasic demo's and would be totally unfair to this challenge..

thanks mick :)

[Big C.]

hey mick,

thx for comment...

a 2 player version would be good i think

yes indeed but it increase the challenge requirements  ;)...  we will see...  :)

Hint for you: I've updated my entry post...

Big C.

[micky4fun]

Hi Big C.

Thanks for update , ile look forward to end result , nive to see how other coders do things , always pick up tips etc

thank for entry

mick :)

[monkeybot]

here is a snake i knocked up.

I can get to about 400...just

PlayBASIC Code: [Select]

; PROJECT : snake
; AUTHOR  : Monkeybot
; CREATED : 28/09/2009
; EDITED  : 29/09/2009
; ---------------------------------------------------------------------
;TODO
;Function display() change this to linked list
;
;
explicit on
constant startLevel=5
constant Debug=0
constant maxLength=2000
constant pillnum=9
Constant pillsize=5
Constant up=3
Constant down=1
Constant left=4
Constant right=2
local ws
if (screenmodeExist(800,600,16)) then ws=false
if(ScreenModeExist(1366,768,16)) then ws=true;;

if ws=true 
   openscreen 1366,768,16,2
else 
   openscreen 800,600,16,2
endif


global highscore=0
do
  global score=0
  global dead=0
  global gamespeed#=startlevel ;fps
  setfps(50)
  global gameloop=timer()
  global countdownTimer=timer()
  global radius#=10
  global sHeight=getscreenheight()
  global sWidth=getscreenwidth()
  global speed=(radius#*2)-2
  global length=6
  global count=0
  global dir=0
  global txtdisplay=0
  global time=0
  global txtX,txtY,txts$
  loadfont "ariel",1,40,1
  loadfont "ariel",2,20,1
  setfont 2
  type snakebody 
     x,y,radius#,colour
  endtype 

  type pills
     x,y,value,display
  endtype
  dim sb(maxLength) as snakebody
  dim pill1(pillnum) as pills
      prepSnake()
      preppills()

          repeat 
               cls 0 
               score=length+gamespeed#*10
               readkeys()
               if timer()>gameloop then dosnake()
               displaypills()
               checkpills()
               displaySnake()
               displayScore()
               if txtdisplay=1 then display()
               increaseDiff()
               if debug then debugInfo()
               displayframe()
               eyes()
                   ;circlec sb(0).x,sb(0).y,4,0,$f0f0f0
               sync
          until dead
      local x,y
      x=swidth/2
      y=sheight/2
      setfont 1
      cls 0
      ink $ff0000
       
      centertext x,y-40,"YOU ARE DEAD!!!!!!!"
      centertext x,y,"You got "+str$(score)
      if score>highscore then CenterText x,y+40,"Woooooo Highscore":highscore=score
      centertext x,y+80,"press any key or Escape to quit"
      sync
      wait 1000
      waitnokey
      waitkey
loop
function eyes()
   local x,y,angle#,xx#,yy#
   ;circlec sb(0).x,sb(0).y,4,0,$f0f0f0
   x=sb(0).x
   y=sb(0).y
   angle#=(dir-1)*90
   ink $ff00ff
   xx#= x+(sin(angle#))*10
   yy#= y+(cos(angle#))*10
   circle xx#,yy#,5,0
   line x,y,xx#,yy#
   ;circle (x+radius#)+sin(angle),(y+radius#)+cos(angle),5,0
endfunction

Function increaseDiff()
local l
     if timer()>countdownTimer
        if gamespeed#<10 then gamespeed#=gamespeed#+0.4;+l)
        countdownTimer=timer()+30000  
     endif
EndFunction

Function readkeys()
local k
shitter:
k=scancode()
    if k=200 then dir=up
    if k=208 then dir=down
    if k=203 then dir=left
    if k=205 then dir=right
    if k=57 and length<maxLength then length=length+1;:moveVars()
    if k=25 then waitnokey:waitkey
EndFunction


Function movevars()
local q
      for q=length-1 to 0 step-1          
          sb(q+1).x=sb(q).x
          sb(q+1).y=sb(q).y
         sb(q+1).radius#=sb(q).radius#
         sb(q+1).colour=sb(q).colour
         sb(q).colour=$00ff00
          
      next
EndFunction


Function displaySnake()
local q
ink sb(0).colour=$00ff00
    for q=0 to length
        ink sb(q).colour

Login required to view complete source code

[Big C.]

n1 one monkeybot and very fast  :)

[kevin]

Yeah, that's a good one.

[micky4fun]

Hi , monkeybot 

not quite got 400 yet , but nearly there ,, nice program

mick :)

[monkeybot]

Thanks for the comments. :)