Here's a port of an n6 example game. Hopefully you can find some clues by looking at the code 
I don't remember why I implemented the game like this, and probably there are smarter ways.
I don't remember why I implemented the game like this, and probably there are smarter ways.Code:
' Port of n6 example game.
SNAKE_MAX_LENGTH = 30*40
UP = 1
DOWN = 2
LEFT = 3
RIGHT = 4
snake = dim(SNAKE_MAX_LENGTH, 2)
level = dim(40, 30)
set window "Smape", 320, 240, false, 2
set redraw off
do
snakeLength = 1
snakeHead = 0
snakeDirection = 0
speed = 10
speedCounter = speed
snake[snakeHead][0] = 20
snake[snakeHead][1] = 15
for y = 0 to 29 for x = 0 to 39 level[x][y] = 0
gameOver = false
nextPlupTime = clock()
do
if clock() >= nextPlupTime
if rnd(3) = 0 level[rnd(40)][rnd(30)] = 2
else level[rnd(40)][rnd(30)] = 1
nextPlupTime = clock() + 2000 + rnd(2000)
endif
if keydown(38) and snakeDirection <> DOWN snakeDirection = UP
if keydown(40) and snakeDirection <> UP snakeDirection = DOWN
if keydown(37) and snakeDirection <> RIGHT snakeDirection = LEFT
if keydown(39) and snakeDirection <> LEFT snakeDirection = RIGHT
speedCounter = speedCounter - 1
if speedCounter = 0
prev = snakeHead
if snakeDirection > 0 snakeHead = (snakeHead + 1)%SNAKE_MAX_LENGTH
speedCounter = speed
if snakeDirection = UP
snake[snakeHead][0] = snake[prev][0]
snake[snakeHead][1] = snake[prev][1] - 1
elseif snakeDirection = DOWN
snake[snakeHead][0] = snake[prev][0]
snake[snakeHead][1] = snake[prev][1] + 1
elseif snakeDirection = LEFT
snake[snakeHead][0] = snake[prev][0] - 1
snake[snakeHead][1] = snake[prev][1]
elseif snakeDirection = RIGHT
snake[snakeHead][0] = snake[prev][0] + 1
snake[snakeHead][1] = snake[prev][1]
endif
x = snake[snakeHead][0]
y = snake[snakeHead][1]
if x < 0 or x >= 40 or y < 0 or y >= 30
gameOver = true
else
if level[x][y] > 0
snakeLength = snakeLength + 1
if level[x][y] = 2 speed = max(speed - 1, 0)
level[x][y] = 0
endif
endif
endif
set color 0, 0, 0
cls
for y = 0 to 29
for x = 0 to 39
if level[x][y] = 1
set color 0, 255, 0
draw rect x*8, y*8, 8, 8 , true
elseif level[x][y] = 2
set color 255, 0, 0
draw rect x*8, y*8, 8, 8, true
endif
next
next
set color 255, 255, 255
set caret 0, 0
x = snake[snakeHead][0]
y = snake[snakeHead][1]
for i = snakeHead to snakeHead - snakeLength + 1
j = i
if j < 0 then j = j + SNAKE_MAX_LENGTH
draw rect snake[j][0]*8, snake[j][1]*8, 8, 8, true
if i <> snakeHead
if snake[j][0] = x and snake[j][1] = y then gameOver = true
endif
next
wait 10
redraw
until gameOver
loop