Snake Wall Collision

[Mr. T]

I want my snake to exit when it collides with the black walls surrounding the screen. What am I doing wrong in my whatdotcolour collision detection? Please Explain. Thanks.
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%variable declaration
View.Set ("graphics:400;300")
var box1 : int := 0
var box2 := maxy
var box3 := maxx
var box4 := 0
var col : int := 31
var countdown : int := 6
var ballx1 : int := 200
var bally1 : int := 150
var ballsize : int := 5
var move, move2, move3, move4 := false
var key : array char of boolean
move3 := true %starting direction of snake

%gives time for user to get ready
loop
locate (9, 20)
put "Starting in...", countdown - 1
delay (300)
countdown := countdown - 1
cls
exit when countdown = 0
end loop

%ball movement
loop
drawbox (box1, box2, box3, box4, 7)
drawfilloval (ballx1, bally1, ballsize, ballsize, col)
if move then
bally1 += 5
elsif move2 then
bally1 -= 5
elsif move3 then
ballx1 += 5
elsif move4 then
ballx1 -= 5
end if

Input.KeyDown (key)
if key (KEY_UP_ARROW) then %if up arrow is pressed
move2 := false
move3 := false
move4 := false
move := true
elsif key (KEY_DOWN_ARROW) then %if down arrow is pressed
move := false
move3 := false
move4 := false
move2 := true
elsif key (KEY_RIGHT_ARROW) then %if right arrow is pressed
move := false
move2 := false
move4 := false
move3 := true
elsif key (KEY_LEFT_ARROW) then %if left arrow is pressed
move := false
move2 := false
move4 := true
move3 := false
end if
drawfilloval (ballx1, bally1, ballsize, ballsize, 12) %deletes the tail
delay (100)
if whatdotcolour (ballx1, bally1) = black then
exit
end if
end loop

[Naveg]

Its because of the way youre increments work. The centre of the circle never actually touches the frame, just skips over it.

[Mr. T]

how would I fix that problem?

[Token]

yah, the problem is that
if whatdotcolour (ballx1, bally1) = black then
dosent touch the color, its the center of the circle, you have to do

if whatdotcolour (ballx1, bally1) = black then
and then add/subtract the radius +1 to the axis that the snake is moving

[Mr. T]

I dont understand how to work with radii, can u explain. with actual code

[Token]

I had to change the way you drew the borded because it moved 5 pixels per move, look at the if statement at the bottom, thats the colision

code:

%variable declaration View.Set ("graphics:400;300") var box1 : int := 0 var box2 := maxy var box3 := maxx var box4 := 0 var col : int := 31 var countdown : int := 6 var ballx1 : int := 200 var bally1 : int := 150 var ballsize : int := 5 var move, move2, move3, move4 := false var key : array char of boolean move3 := true %starting direction of snake %gives time for user to get ready loop     locate (9, 20)     put "Starting in...", countdown - 1     delay (300)     countdown := countdown - 1     cls     exit when countdown = 0 end loop %ball movement     drawfillbox (0, 0, maxx, maxy, black)     drawfillbox (5, 5, maxx - 5, maxy - 5, white) loop     drawfilloval (ballx1, bally1, ballsize, ballsize, col)     if move then         bally1 += 5     elsif move2 then         bally1 -= 5     elsif move3 then         ballx1 += 5     elsif move4 then         ballx1 -= 5     end if     Input.KeyDown (key)     if key (KEY_UP_ARROW) then %if up arrow is pressed         move2 := false         move3 := false         move4 := false         move := true     elsif key (KEY_DOWN_ARROW) then %if down arrow is pressed         move := false         move3 := false         move4 := false         move2 := true     elsif key (KEY_RIGHT_ARROW) then %if right arrow is pressed         move := false         move2 := false         move4 := false         move3 := true     elsif key (KEY_LEFT_ARROW) then %if left arrow is pressed         move := false         move2 := false         move4 := true         move3 := false     end if     drawfilloval (ballx1, bally1, ballsize, ballsize, 12) %deletes the tail     delay (100)     if move = true and whatdotcolour (ballx1, bally1 + 6) = black then         exit     elsif move2 = true and whatdotcolour (ballx1, bally1 - 6) = black then         exit     elsif move3 = true and whatdotcolour (ballx1 + 6, bally1) = black then         exit     elsif move4 = true and whatdotcolour (ballx1 - 6, bally1 + 6) = black then         exit     end if end loop

[Mr. T]

thnx for the help.
i decided to change how my game would work in order to avoid whatdotcolour.
originally i wanted my black border to shrink.
but now instead, ill juss adjust View.Set after every level.
thanks anyways

[Token]

for games like this whatdotcolor is really effective, i wouldent avoid it if i were you, the shrinking of the border could be done really easily just by putting the drawbox that draws the border inside the loop and adding a counter to make it shrink, also you could have little dots randomly apearing and when u hit one it makes the border open up more, so give whatdotcolor a shot because its the easiest approach i see

check this out

code:

%variable declaration View.Set ("graphics:400;300,offscreeononly") var box1 : int := 0 var box2 := maxy var box3 := maxx var box4 := 0 var col : int := 31 var countdown : int := 6 var ballx1 : int := 200 var bally1 : int := 150 var ballsize : int := 5 var move, move2, move3, move4 := false var key : array char of boolean var bordercount : real := 0 var randx, randy : int move3 := true %starting direction of snake process dots     loop         randx := Rand.Int (5 + round (bordercount), maxx - 5 - round (bordercount))         randy := Rand.Int (5 + round (bordercount), maxy - 5 - round (bordercount))         drawfilloval (randx, randy, 15, 15, brightred)         View.Update         delay (5000)         cls     end loop end dots %gives time for user to get ready loop     locate (9, 20)     put "Starting in...", countdown - 1     View.Update     delay (300)     countdown := countdown - 1     cls     exit when countdown = 0 end loop %ball movement drawfillbox (0, 0, maxx, maxy, black) drawfillbox (5 + round (bordercount), 5 + round (bordercount), maxx - 5 - round (bordercount), maxy - 5 - round (bordercount), white) fork dots loop     bordercount += .25     drawbox (5 + round (bordercount), 5 + round (bordercount), maxx - 5 - round (bordercount), maxy - 5 - round (bordercount), black)     drawfilloval (ballx1, bally1, ballsize, ballsize, col)     View.Update     if move then         bally1 += 5     elsif move2 then         bally1 -= 5     elsif move3 then         ballx1 += 5     elsif move4 then         ballx1 -= 5     end if     Input.KeyDown (key)     if key (KEY_UP_ARROW) then %if up arrow is pressed         move2 := false         move3 := false         move4 := false         move := true     elsif key (KEY_DOWN_ARROW) then %if down arrow is pressed         move := false         move3 := false         move4 := false         move2 := true     elsif key (KEY_RIGHT_ARROW) then %if right arrow is pressed         move := false         move2 := false         move4 := false         move3 := true     elsif key (KEY_LEFT_ARROW) then %if left arrow is pressed         move := false         move2 := false         move4 := true         move3 := false     end if     drawfilloval (ballx1, bally1, ballsize, ballsize, 12) %deletes the tail     delay (50)     if move = true and whatdotcolour (ballx1, bally1 + 6) = black then         exit     elsif move2 = true and whatdotcolour (ballx1, bally1 - 6) = black then         exit     elsif move3 = true and whatdotcolour (ballx1 + 6, bally1) = black then         exit     elsif move4 = true and whatdotcolour (ballx1 - 6, bally1 + 6) = black then         exit     end if     if move = true and whatdotcolour (ballx1, bally1 + 6) = brightred then         cls         bordercount -= 20     elsif move2 = true and whatdotcolour (ballx1, bally1 - 6) = brightred then         cls         bordercount -= 20     elsif move3 = true and whatdotcolour (ballx1 + 6, bally1) = brightred then         cls         bordercount -= 20     elsif move4 = true and whatdotcolour (ballx1 - 6, bally1 + 6) = brightred then         cls         bordercount -= 20     end if end loop

[Mr. T]

lol, thats very glitchy

[Cervantes]

Yep. Token, you shouldn't be using a process for that. What's worse, because you're using a process, you've got TWO View.Updates. That's never good. It gives you some flickering (especially because you don't know when the View.Update in the process actually works).

I cleaned up the code. Namely, I took out the process, and eliminated whatdotcolour detection. Token, with you're approach to whatdotcolour detection, you've effectively got four points around the circle that you are checking for collisions. You're not checking anything to do with diagonals. See, if you use the Math.Distance approach for circular collisions, it's as though you've got an infinite amount of checking points around the player. I don't know if you want your snake to be circular, Pwned, but if you do, this is the way to go.I also changed the variables around so that the player and the clear ball (the big red one) are in record format. Lastly, I changed around the loop structure such that all input and input analyzing is grouped together, all drawing is grouped together, and all the other, necessary stuff (ie. collision detection) is grouped together.

Turing:

%variable declaration View.Set ("graphics:400;300,offscreenonly") colourback (black) var key : array char of boolean var bordercount : real := 0 var player :     record         x, y : real         DIR : string         radius : int         speed : int  %number of pixels the player moves each time through the loop     end record player.x := maxx div 2 player.y := maxy div 2 player.DIR := "U" player.radius := 9 player.speed := 5 var clearBall :     record         x, y : real         radius : int     end record clearBall.x := -100 clearBall.y := -100       %offscreen clearBall.radius := 15 var timeLast := 0 %time that the last big red circle was created. var timeDelay := 5000 %delay in producing the red circles.  Measured in milliseconds loop     exit when player.x - player.radius < bordercount or player.x + player.radius > maxx - bordercount or player.y - player.radius < bordercount or player.y + player.radius > maxy - bordercount     if Math.Distance (player.x, player.y, clearBall.x, clearBall.y) < player.radius + clearBall.radius then %collide with clearBAll         bordercount -= 20         clearBall.x := -100 %move it offscreen         clearBall.y := -100     end if     if Time.Elapsed > timeLast + timeDelay then         timeLast := Time.Elapsed         clearBall.x := Rand.Int (5 + round (bordercount), maxx - 5 - round (bordercount))         clearBall.y := Rand.Int (5 + round (bordercount), maxy - 5 - round (bordercount))     end if     bordercount += .25     %---- input and movement     Input.KeyDown (key)     if key (KEY_UP_ARROW) then %if up arrow is pressed         player.DIR := "U"     elsif key (KEY_DOWN_ARROW) then %if down arrow is pressed         player.DIR := "D"     elsif key (KEY_RIGHT_ARROW) then %if right arrow is pressed         player.DIR := "R"     elsif key (KEY_LEFT_ARROW) then %if left arrow is pressed         player.DIR := "L"     end if     case player.DIR of         label "U" :             player.y += player.speed         label "D" :             player.y -= player.speed         label "L" :             player.x -= player.speed         label "R" :             player.x += player.speed         label :     end case     %drawing     cls     Draw.FillBox (round (bordercount), round (bordercount), round (maxx - bordercount), round (maxy - bordercount), white)     drawfilloval (round (clearBall.x), round (clearBall.y), 15, 15, brightred)     %the big red circle     drawfilloval (round (player.x), round (player.y), player.radius, player.radius, 12)     %player     View.Update     delay (50) end loop