Help with Snake Game

[josh]

Hey, I am making a snake game for my FP with my friend. I have gotten it so that the snake moves continuoulsy in the direction last hit by the user, it can eat an orange, and get bigger, however it does not get bigger properly and I can't get it so that when you turn just he front of the snake bends and hte back follows the path.

Me and my compsci teacher are stumped as to what we need to do. Here is the code:

code:

%declare variables here var move : array char of boolean        %what direction the user wants to move in var snakeX : array 1 .. 15 of int var snakeY : array 1 .. 15 of int var snakeSizeX : array 1 .. 15 of int var snakeSizeY : array 1 .. 15 of int var snakeDirection : array 1 .. 15 of string var segmentCount : int var ox, oy : int var sleft, sright, stop, sbottom : int var oleft, oright, otop, obottom : int var collisionOrange : boolean := false var ans : string (1) var totalsize : int := 20 %size of the snake var speed : int := 1 %Define variables snakeSizeX (1) := 20 snakeSizeY (1) := 0 snakeDirection (1) := "right" segmentCount := 1 snakeX (1) := 30 snakeY (1) := 30 for i : 1 .. 15     snakeSizeX (i) := 20     snakeSizeY (i) := 20 end for loop     randint (ox, 10, 200)     randint (oy, 10, 200)     loop         Draw.FillBox (ox, oy, ox + 20, oy + 20, 4)         %get the direction         Input.KeyDown (move)         if move (KEY_UP_ARROW) then             for i : 1 .. segmentCount - 1                 snakeDirection (i + 1) := snakeDirection (i)             end for             snakeDirection (1) := "up"             if snakeSizeY (1) < totalsize then                 snakeSizeY (1) += 1                 if snakeDirection (segmentCount) = "up" or snakeDirection (segmentCount) = "down" then                     snakeSizeY (segmentCount) -= 1                 else                     snakeSizeX (segmentCount) -= 1                 end if             end if         elsif move (KEY_DOWN_ARROW) then             for i : 1 .. segmentCount - 1                 snakeDirection (i + 1) := snakeDirection (i)             end for             snakeDirection (1) := "down"             if snakeSizeY (1) < totalsize then                 snakeSizeY (1) += 1                 if snakeDirection (segmentCount) = "up" or snakeDirection (segmentCount) = "down" then                     snakeSizeY (segmentCount) -= 1                 else                     snakeSizeX (segmentCount) -= 1                 end if             end if         elsif move (KEY_RIGHT_ARROW) then             for i : 1 .. segmentCount - 1                 snakeDirection (i + 1) := snakeDirection (i)             end for             snakeDirection (1) := "right"             if snakeSizeX (1) < totalsize then                 snakeSizeX (1) += 1                 if snakeDirection (segmentCount) = "up" or snakeDirection (segmentCount) = "down" then                     snakeSizeY (segmentCount) -= 1                 else                     snakeSizeX (segmentCount) -= 1                 end if             end if         elsif move (KEY_LEFT_ARROW) then             for i : 1 .. segmentCount - 1                 snakeDirection (i + 1) := snakeDirection (i)             end for             snakeDirection (1) := "left"             if snakeSizeX (1) < totalsize then                 snakeSizeX (1) += 1                 if snakeDirection (segmentCount) = "up" or snakeDirection (segmentCount) = "down" then                     snakeSizeY (segmentCount) -= 1                 else                     snakeSizeX (segmentCount) -= 1                 end if             end if         end if         %allow snake to continue in direction         if snakeDirection (segmentCount) = "up" then             for i : 1 .. segmentCount - 1                 snakeY (i + 1) := snakeY (i)                 snakeX (i + 1) := snakeX (i)             end for             if segmentCount = 2 then                 snakeY (2) := snakeY (1)                 snakeX (2) := snakeX (1)             end if             snakeY (1) += speed         elsif snakeDirection (segmentCount) = "right" then             for i : 1 .. segmentCount - 1                 snakeX (i + 1) := snakeX (i)                 snakeY (i + 1) := snakeY (i)             end for             if segmentCount = 2 then                 snakeX (2) := snakeX (1)                 snakeY (2) := snakeY (1)             end if                         snakeX (1) += speed         elsif snakeDirection (segmentCount) = "down" then             for i : 1 .. segmentCount - 1                 snakeX (i + 1) := snakeX (i)                 snakeY (i + 1) := snakeY (i)             end for             if segmentCount = 2 then                 snakeY (2) := snakeY (1)                 snakeX (2) := snakeX (1)             end if             snakeY (1) -= speed         elsif snakeDirection (segmentCount) = "left" then             for i : 1 .. segmentCount - 1                 snakeX (i + 1) := snakeX (i)                 snakeY (i + 1) := snakeY (i)             end for             if segmentCount = 2 then                 snakeX (2) := snakeX (1)                 snakeY (2) := snakeY (1)             end if             snakeX (1) -= speed         end if         %set the right left top and bottom         sleft := snakeX (1)         sright := snakeX (1) + totalsize         sbottom := snakeY (1)         stop := snakeY (1) + 20         oleft := ox         oright := ox + 20         obottom := oy         otop := oy + 20         if stop > obottom and sbottom < otop then             if sright > oleft and sleft < oright then                 collisionOrange := true             end if         end if         for i : 1 .. segmentCount             Draw.FillBox (snakeX (i), snakeY (i), snakeX (i) + snakeSizeX (i), snakeY (i) + snakeSizeY (i), 10)         end for         delay (10)         cls         exit when collisionOrange = true     end loop     totalsize += 10     segmentCount += 1     snakeDirection (segmentCount) := snakeDirection (segmentCount - 1)     collisionOrange := false     delay (100) end loop

a few things my teacher helped me with I don't understand 100% but most of it I do.

[Cervantes]

I hope you realize that's not what Snake is supposed to look like. Are you trying to go for this, new, style of Snake? Also, Snake is supposed to work on a grid, such that each "body part" of the snake is the size of one grid square. Right now, you seem to be doing it without a grid (I guess you could say you're grid size is 1).
There's some Snake games on compsci.ca, search for them. There's also a ton of help threads regarding snake right now, they might contain useful inforamtion. If not, let us know

[josh]

It does not look like snake because It is not working yet.

it can't get the snake to bend properly and follow the head, and I can't figure out why both sides of the square get larger

[Cervantes]

When in doubt, refer to Zylum's source.

zylum:

proc moveSnake     var tempx, tempy : int     if snake (1).x = foodx and snake (1).y = foody then         score += scoreInc         moveFood         new snake, upper (snake) + 1     end if     tempx := snake (1).x     tempy := snake (1).y     for decreasing i : upper (snake) .. 2         snake (i).x := snake (i - 1).x         snake (i).y := snake (i - 1).y     end for     snake (1).x := tempx + snkData.dx     snake (1).y := tempy + snkData.dy end moveSnake

Also, note the use of new. He's using a flexible array (in conjunction with records) to get the job done. You should probably do the same, because, otherwise, you'll get an error when the snake gets more than 15 parts (you've got your arrays 1 .. 15, currently).

The whole thread can be found here:

[josh]

I actually just finished looking at that and I have sent him a PM.

I also just read the tutorial on records a few hours ago and was considering htem using them, adnd I also read the one on flexibl arrays.

Tomoorow I am gunna try and start from scratch to get one that works on a grid system. I just don't undersntandt he part in zylums codenear the end witht the three drawfillbox's.

[Amreen]

kool

[josh]

uh...not really but thanx n e way.

I have totally re-wrote it with my partner, it still does not look like the traditional snake (it is not on a grid) but it will be o.k. for handing in. I am definnatly gunna try and make an actual good version of snake when i don't have the time constraints imposed by school.

The only thing I am having trouble with is the collision detection because they are circles and they are not on a grid.

[Cervantes]

Circle collision is easy.

code:

if Math.Distance (x1, y1, x2, y2) < radius1 + radius 2 then   collision := true end if

As for the three drawfillboxes in zylums code:
the first is for drawing that green background;
the second is for drawing the food;
the third is for drawing the snake.
What's probably confusing you is all the variables inside the draw commands. Really, it's rather simple. Just understand that the variables for the locations of the snake / food etc. are very small, like 1 to 20 or something. So, he multiplies it by a constant (gridData.width) to, essentially, enlarge it.

Take this fully customizable grid:

code:

const screenWidth := 600 const screenHeight := 600 View.Set ("graphics:" + intstr (screenWidth) + ";" + intstr (screenHeight)) const gridX := 8 %number of squares const gridY := 8 const gridOffsetX1 := 100 %grid will go from (gridOffsetX1, gridOffsetY1) to (gridOffsetX2, gridOffsetY2) const gridOffsetX2 := maxx - 100 const gridOffsetY1 := 100 const gridOffsetY2 := maxy - 100 const gridWidth := round ((screenWidth - gridOffsetX1 - (maxx - gridOffsetX2)) / gridX) %size of each grid, in pixels const gridHeight := round ((screenHeight - gridOffsetY1 - (maxy - gridOffsetY2)) / gridY) var grid : array 0 .. gridX - 1, 0 .. gridY - 1 of boolean % - 1 because the array starts from 0, not 1 for ix : 0 .. upper (grid, 1)     for iy : 0 .. upper (grid, 1)         grid (ix, iy) := false     end for end for %just to show the grid in action, make some squares "true".  Later, "true" squares will be filled in. for i : 1 .. 10     grid (Rand.Int (0, upper (grid, 1)), Rand.Int (0, upper (grid, 1))) := true end for %draw the lines of the grid for x : 0 .. upper (grid, 1) + 1 %add one to draw the last line.  Try taking it away.     drawline (x * gridWidth + gridOffsetX1, gridOffsetY1, x * gridWidth + gridOffsetX1, gridOffsetY2, black) end for for y : 0 .. upper (grid, 2) + 1     drawline (gridOffsetX1, y * gridHeight + gridOffsetY1, gridOffsetX2, y * gridHeight + gridOffsetY1, black) end for %colour the "true" squares black for x : 0 .. upper (grid, 1)     for y : 0 .. upper (grid, 1)         if grid (x, y) then             drawfillbox (x * gridWidth + gridOffsetX1, y * gridHeight + gridOffsetY1, x * gridWidth + gridWidth + gridOffsetX1, y * gridHeight + gridHeight + gridOffsetY1, black)         end if     end for end for

[josh]

thanks for the help cervantes. It was the variables that where confusing me, what is the advantage though of using smaller variables and multiplying by a constant?

I have never used the Math functions before so I was going to use the method that tony wrote about in a tutorial in the turing section, but this looks alot easier

[Cervantes]

The advantage of using smaller variables and multiplying by a constant:
1.) It's easier to understand, for yourself. Would you rather be thinking about 175 being one grid more than 150, or 7 being one grid space more than 6.
2.) It's easier for comparasin's, for collision. Same reason as above.

If you are going for the grid style, as opposed to the grid size one style (that you had at first), you're going to either store information in terms of large numbers and divide by a constant to compare them (or compare them as is, but that's annoying too), or store information as small numbers, compare them easily, and then multiply by a constant to draw them to the screen.

It's somewhat hard to explain. I hope I did a semi-decent job
-Cervantes

[cool dude]

well, well, well, always wanting to go your way josh (lol). i told u thats not how snake looks and we should go my way.

code:

% Declare variables type snakeDat :     record         x : int         y : int     end record var snake : flexible array 1 .. 2 of snakeDat var key : string (1) %the users key button variable var move : string := "MOVE" %variable for the way the snake is moving var ox, oy : int     %holds the orange var orangeGood : boolean := false var score : int := 0 var orangeCollision : boolean := false % initialize variables snake (1).x := maxx div 2 snake (1).y := maxy div 2 %procedure for the snake going up proc snake_up     snake (1).y += 20     drawfilloval (snake (1).x, snake (1).y, 10, 10, 41)   %snake head     drawfilloval (snake (1).x - 4, snake (1).y + 4, 2, 2, black)   %eyes     drawfilloval (snake (1).x + 4, snake (1).y + 4, 2, 2, black)   %eyes     %drawfilloval (snake (1).x, snake (1).y - 20, 10, 10, 12)       %Snake following     View.Update     %updates the graphics on screen     move := "UP" end snake_up %procedure for the snake going down proc snake_down     snake (1).y -= 20     drawfilloval (snake (1).x, snake (1).y, 10, 10, 41)   %snake head     drawfilloval (snake (1).x - 4, snake (1).y - 4, 2, 2, black)   %eyes     drawfilloval (snake (1).x + 4, snake (1).y - 4, 2, 2, black)   %eyes     %drawfilloval (snake (1).x, snake (1).y + 20, 10, 10, 12)       %Snake following     View.Update     %updates the graphics on screen     move := "DOWN" end snake_down %procedure for the snake going left proc snake_left     snake (1).x -= 20     drawfilloval (snake (1).x, snake (1).y, 10, 10, 41)   %snake head     drawfilloval (snake (1).x - 4, snake (1).y + 4, 2, 2, black)   %eyes     drawfilloval (snake (1).x - 4, snake (1).y - 4, 2, 2, black)   %eyes     %drawfilloval (snake (1).x + 20, snake (1).y, 10, 10, 12)       %Snake following     View.Update     %updates the graphics on screen     move := "LEFT" end snake_left %procedure for the snake going right proc snake_right     snake (1).x += 20     drawfilloval (snake (1).x, snake (1).y, 10, 10, 41)     %snake head     drawfilloval (snake (1).x + 4, snake (1).y + 4, 2, 2, black)     %eyes     drawfilloval (snake (1).x + 4, snake (1).y - 4, 2, 2, black)     %eyes     %drawfilloval (snake (1).x - 20, snake (1).y, 10, 10, 12)         %Snake following     View.Update     %updates the graphics on screen     move := "RIGHT" end snake_right %procedure to move the snake according to the user's input proc move_snake     if key = KEY_UP_ARROW and move not= "DOWN" then         snake_up     elsif key = KEY_UP_ARROW and move = "DOWN" then         snake_down     elsif key = KEY_DOWN_ARROW and move not= "UP" then         snake_down     elsif key = KEY_DOWN_ARROW and move = "UP" then         snake_up     elsif key = KEY_LEFT_ARROW and move not= "RIGHT" then         snake_left     elsif key = KEY_LEFT_ARROW and move = "RIGHT" then         snake_right     elsif key = KEY_RIGHT_ARROW and move not= "LEFT" then         snake_right     elsif key = KEY_RIGHT_ARROW and move = "LEFT" then         snake_left     end if end move_snake proc update_snake     for i : 2 .. upper (snake)         snake (i).x := snake (i - 1).x         snake (i).y := snake (i - 1).y     end for end update_snake proc make_orange     loop         orangeGood := true         randint (ox, 20, 790)         randint (oy, 20, 590)         for i : 1 .. upper (snake)             if ox = snake (i).x or ox < snake (i).x + 11 or ox > snake (i).x + 11 then                 if oy = snake (i).y or oy < snake (i).y + 11 or oy > snake (i).y + 11 then                     orangeGood := false                 end if             end if         end for         exit when orangeGood = true     end loop end make_orange proc draw_orange     Draw.FillOval (ox, oy, 10, 10, 42) end draw_orange proc draw_snake     for i : 2 .. upper (snake)         Draw.FillOval (snake (i).x, snake (i).y, 10, 10, 12)     end for end draw_snake % proc check_collision %     if snake(1).x + 10 < ox - 10 or snake(1).x - 10 > ox + 10 then %         if snake(1).y + 10 < oy - 10 or snake(1).y - 10 > oy +10 then %             orangeCollision := true %             make_orange %             score += 10 %             new snake, upper (snake) + 1 %         end if %     end if % end check_collision update_snake draw_snake make_orange loop     getch (key)     loop         update_snake         %        check_collision         draw_orange         move_snake         draw_snake         delay (100)         cls         exit when hasch     end loop end loop

the only problem with this is we can't make it eat the actual orange. i know we have to use a grid but what would be better to use whatdotcolour or collision detection. josh and i are arguing about that. as well how would you use those because we tried both but we can't really get it to work.

[Neo]

Whatdotcolour is a form of collision detection. If your going to use circles I'd suggest using circle collision detection using Math.Distance(). Get the distance from the food to the snake's head. If the disttance is less than their radiuses combined then eat the food.

[Cervantes]

Neo wrote:

If your going to use circles I'd suggest using circle collision detection using Math.Distance()

Actually, I would recommend using location comparisons. It's just as easy, and if you ever decide to use squares instead of ovals, it'll be just a matter of changing the draw commands.

[josh]

as you probobly guessed cooldude is my partner.

I tried just changing the draw command but it really messed it up, so there is more to it than that. I like using hte math.function as it seems really simple and it will work.

I would use a gird, but we don't have much time to do this and I don't want to go and re-write the whole code again....

Cervantes what do you mena by location comparisons? i

you mean like this:

code:

sleft := sx         sright := sx + size         sbottom := sy         stop := sy + 20                 oleft := ox         oright := ox + 20         obottom := oy         otop := oy + 20                 if stop > obottom and sbottom < otop then             if sright > oleft and sleft < oright then                 collision := true             end if         end if

[josh]

o.k. so I got the collisoin detectoin working and now the snake grows also but for some reason after it eats an orange the screen sometimes just randomly goes white.

Can n e 1 figure out why? here is the new code:

Turing:

% Declare variables type snakeDat :     record         x : int         y : int     end record var snake : flexible array 1 .. 2 of snakeDat var key : string (1) %the users key button variable var move : string := "MOVE" %variable for the way the snake is moving var ox, oy : int     %holds the orange var orangeGood : boolean := false var score : int := 0 var orangeCollision : boolean := false % initialize variables snake (1).x := maxx div 2 snake (1).y := maxy div 2 %procedure for the snake going up proc snake_up     snake (1).y += 20     drawfilloval (snake (1).x, snake (1).y, 10, 10, 41)   %snake head     drawfilloval (snake (1).x - 4, snake (1).y + 4, 2, 2, black)   %eyes     drawfilloval (snake (1).x + 4, snake (1).y + 4, 2, 2, black)   %eyes     %drawfilloval (snake (1).x, snake (1).y - 20, 10, 10, 12)       %Snake following     View.Update     %updates the graphics on screen     move := "UP" end snake_up %procedure for the snake going down proc snake_down     snake (1).y -= 20     drawfilloval (snake (1).x, snake (1).y, 10, 10, 41)   %snake head     drawfilloval (snake (1).x - 4, snake (1).y - 4, 2, 2, black)   %eyes     drawfilloval (snake (1).x + 4, snake (1).y - 4, 2, 2, black)   %eyes     %drawfilloval (snake (1).x, snake (1).y + 20, 10, 10, 12)       %Snake following     View.Update     %updates the graphics on screen     move := "DOWN" end snake_down %procedure for the snake going left proc snake_left     snake (1).x -= 20     drawfilloval (snake (1).x, snake (1).y, 10, 10, 41)   %snake head     drawfilloval (snake (1).x - 4, snake (1).y + 4, 2, 2, black)   %eyes     drawfilloval (snake (1).x - 4, snake (1).y - 4, 2, 2, black)   %eyes     %drawfilloval (snake (1).x + 20, snake (1).y, 10, 10, 12)       %Snake following     View.Update     %updates the graphics on screen     move := "LEFT" end snake_left %procedure for the snake going right proc snake_right     snake (1).x += 20     drawfilloval (snake (1).x, snake (1).y, 10, 10, 41)     %snake head     drawfilloval (snake (1).x + 4, snake (1).y + 4, 2, 2, black)     %eyes     drawfilloval (snake (1).x + 4, snake (1).y - 4, 2, 2, black)     %eyes     %drawfilloval (snake (1).x - 20, snake (1).y, 10, 10, 12)         %Snake following     View.Update     %updates the graphics on screen     move := "RIGHT" end snake_right %procedure to move the snake according to the user's input proc move_snake     if key = KEY_UP_ARROW and move not= "DOWN" then         snake_up     elsif key = KEY_UP_ARROW and move = "DOWN" then         snake_down     elsif key = KEY_DOWN_ARROW and move not= "UP" then         snake_down     elsif key = KEY_DOWN_ARROW and move = "UP" then         snake_up     elsif key = KEY_LEFT_ARROW and move not= "RIGHT" then         snake_left     elsif key = KEY_LEFT_ARROW and move = "RIGHT" then         snake_right     elsif key = KEY_RIGHT_ARROW and move not= "LEFT" then         snake_right     elsif key = KEY_RIGHT_ARROW and move = "LEFT" then         snake_left     end if end move_snake proc update_snake     for i : 2 .. upper (snake)         snake (i).x := snake (i - 1).x         snake (i).y := snake (i - 1).y     end for end update_snake proc make_orange     loop         orangeGood := true         randint (ox, 20, 790)         randint (oy, 20, 590)         for i : 1 .. upper (snake)             if ox = snake (i).x or ox < snake (i).x + 11 or ox > snake (i).x + 11 then                 if oy = snake (i).y or oy < snake (i).y + 11 or oy > snake (i).y + 11 then                     orangeGood := false                 end if             end if         end for         exit when orangeGood = true     end loop end make_orange proc draw_orange     Draw.FillOval (ox, oy, 10, 10, 42) end draw_orange proc draw_snake     for i : 2 .. upper (snake)         Draw.FillOval (snake (i).x, snake (i).y, 10, 10, 12)     end for end draw_snake procedure check_collision     % if snake (1).x + 10 < ox - 10 or snake (1).x - 10 > ox + 10 then     %     if snake (1).y + 10 < oy - 10 or snake (1).y - 10 > oy + 10 then     %         orangeCollision := true     %         make_orange     %         score += 10     %         new snake, upper (snake) + 1     %     end if     % end if     if Math.Distance (snake(1).x, snake(1).y, ox, oy) < 20 then         orangeCollision := true         make_orange         score += 10         new snake, upper (snake) + 1     end if     end check_collision update_snake draw_snake make_orange loop     getch (key)     loop         check_collision         draw_orange         update_snake         move_snake         draw_snake         locate (1,1)         put score         delay (100)         cls         exit when hasch     end loop end loop

EDIT: I have been looking at this some more and I am wonderng, is it that the new orange is being generated ontop of the new circle being added to the snake?