Snake

From Rosetta Code
Snake is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
This page uses content from Wikipedia. The original article was at Snake_(video_game). The list of authors can be seen in the page history. As with Rosetta Code, the text of Wikipedia is available under the GNU FDL. (See links for details on variance)
Snake is a game where the player maneuvers a line which grows in length every time the snake reaches a food source.
Task

Implement a variant of the Snake game, in any interactive environment, in which a sole player attempts to eat items by running into them with the head of the snake. Each item eaten makes the snake longer and a new item is randomly generated somewhere else on the plane. The game ends when the snake attempts to eat himself.

C++[edit]

Simple Windows console implementation.

SnakeCpp.png
 
#include <windows.h>
#include <ctime>
#include <iostream>
#include <string>
 
const int WID = 60, HEI = 30, MAX_LEN = 600;
enum DIR { NORTH, EAST, SOUTH, WEST };
 
class snake {
public:
snake() {
console = GetStdHandle( STD_OUTPUT_HANDLE ); SetConsoleTitle( "Snake" );
COORD coord = { WID + 1, HEI + 2 }; SetConsoleScreenBufferSize( console, coord );
SMALL_RECT rc = { 0, 0, WID, HEI + 1 }; SetConsoleWindowInfo( console, TRUE, &rc );
CONSOLE_CURSOR_INFO ci = { 1, false }; SetConsoleCursorInfo( console, &ci );
}
void play() {
std::string a;
while( 1 ) {
createField(); alive = true;
while( alive ) { drawField(); readKey(); moveSnake(); Sleep( 50 ); }
COORD c = { 0, HEI + 1 }; SetConsoleCursorPosition( console, c );
SetConsoleTextAttribute( console, 0x000b );
std::cout << "Play again [Y/N]? "; std::cin >> a;
if( a.at( 0 ) != 'Y' && a.at( 0 ) != 'y' ) return;
}
}
private:
void createField() {
COORD coord = { 0, 0 }; DWORD c;
FillConsoleOutputCharacter( console, ' ', ( HEI + 2 ) * 80, coord, &c );
FillConsoleOutputAttribute( console, 0x0000, ( HEI + 2 ) * 80, coord, &c );
SetConsoleCursorPosition( console, coord );
int x = 0, y = 1; for( ; x < WID * HEI; x++ ) brd[x] = 0;
for( x = 0; x < WID; x++ ) {
brd[x] = brd[x + WID * ( HEI - 1 )] = '+';
}
for( ; y < HEI; y++ ) {
brd[0 + WID * y] = brd[WID - 1 + WID * y] = '+';
}
do {
x = rand() % WID; y = rand() % ( HEI >> 1 ) + ( HEI >> 1 );
} while( brd[x + WID * y] );
brd[x + WID * y] = '@';
tailIdx = 0; headIdx = 4; x = 3; y = 2;
for( int c = tailIdx; c < headIdx; c++ ) {
brd[x + WID * y] = '#';
snk[c].X = 3 + c; snk[c].Y = 2;
}
head = snk[3]; dir = EAST; points = 0;
}
void readKey() {
if( GetAsyncKeyState( 39 ) & 0x8000 ) dir = EAST;
if( GetAsyncKeyState( 37 ) & 0x8000 ) dir = WEST;
if( GetAsyncKeyState( 38 ) & 0x8000 ) dir = NORTH;
if( GetAsyncKeyState( 40 ) & 0x8000 ) dir = SOUTH;
}
void drawField() {
COORD coord; char t;
for( int y = 0; y < HEI; y++ ) {
coord.Y = y;
for( int x = 0; x < WID; x++ ) {
t = brd[x + WID * y]; if( !t ) continue;
coord.X = x; SetConsoleCursorPosition( console, coord );
if( coord.X == head.X && coord.Y == head.Y ) {
SetConsoleTextAttribute( console, 0x002e );
std::cout << 'O'; SetConsoleTextAttribute( console, 0x0000 );
continue;
}
switch( t ) {
case '#': SetConsoleTextAttribute( console, 0x002a ); break;
case '+': SetConsoleTextAttribute( console, 0x0019 ); break;
case '@': SetConsoleTextAttribute( console, 0x004c ); break;
}
std::cout << t; SetConsoleTextAttribute( console, 0x0000 );
}
}
std::cout << t; SetConsoleTextAttribute( console, 0x0007 );
COORD c = { 0, HEI }; SetConsoleCursorPosition( console, c );
std::cout << "Points: " << points;
}
void moveSnake() {
switch( dir ) {
case NORTH: head.Y--; break;
case EAST: head.X++; break;
case SOUTH: head.Y++; break;
case WEST: head.X--; break;
}
char t = brd[head.X + WID * head.Y];
if( t && t != '@' ) { alive = false; return; }
brd[head.X + WID * head.Y] = '#';
snk[headIdx].X = head.X; snk[headIdx].Y = head.Y;
if( ++headIdx >= MAX_LEN ) headIdx = 0;
if( t == '@' ) {
points++; int x, y;
do {
x = rand() % WID; y = rand() % ( HEI >> 1 ) + ( HEI >> 1 );
} while( brd[x + WID * y] );
brd[x + WID * y] = '@'; return;
}
SetConsoleCursorPosition( console, snk[tailIdx] ); std::cout << ' ';
brd[snk[tailIdx].X + WID * snk[tailIdx].Y] = 0;
if( ++tailIdx >= MAX_LEN ) tailIdx = 0;
}
bool alive; char brd[WID * HEI];
HANDLE console; DIR dir; COORD snk[MAX_LEN];
COORD head; int tailIdx, headIdx, points;
};
int main( int argc, char* argv[] ) {
srand( static_cast<unsigned>( time( NULL ) ) );
snake s; s.play(); return 0;
}
 

Java[edit]

See Snake/Java.

JavaScript[edit]

You need the P5 Library to run this code!

 
const L = 1, R = 2, D = 4, U = 8;
var block = 24, wid = 30, hei = 20, frameR = 7, fruit, snake;
function Snake() {
this.length = 1;
this.alive = true;
this.pos = createVector( 1, 1 );
this.posArray = [];
this.posArray.push( createVector( 1, 1 ) );
this.dir = R;
this.draw = function() {
fill( 130, 190, 0 );
var pos, i = this.posArray.length - 1, l = this.length;
while( true ){
pos = this.posArray[i--];
rect( pos.x * block, pos.y * block, block, block );
if( --l == 0 ) break;
}
}
this.eat = function( frut ) {
var b = this.pos.x == frut.x && this.pos.y == frut.y;
if( b ) this.length++;
return b;
}
this.overlap = function() {
var len = this.posArray.length - 1;
for( var i = len; i > len - this.length; i-- ) {
tp = this.posArray[i];
if( tp.x === this.pos.x && tp.y === this.pos.y ) return true;
}
return false;
}
this.update = function() {
if( !this.alive ) return;
switch( this.dir ) {
case L:
this.pos.x--; if( this.pos.x < 1 ) this.pos.x = wid - 2;
break;
case R:
this.pos.x++; if( this.pos.x > wid - 2 ) this.pos.x = 1;
break;
case U:
this.pos.y--; if( this.pos.y < 1 ) this.pos.y = hei - 2;
break;
case D:
this.pos.y++; if( this.pos.y > hei - 2 ) this.pos.y = 1;
break;
}
if( this.overlap() ) { this.alive = false; } else {
this.posArray.push( createVector( this.pos.x, this.pos.y ) );
if( this.posArray.length > 5000 ) { this.posArray.splice( 0, 1 ); }
}
}
}
function Fruit() {
this.fruitTime = true;
this.pos = createVector();
this.draw = function() {
fill( 200, 50, 20 );
rect( this.pos.x * block, this.pos.y * block, block, block );
}
 
this.setFruit = function() {
this.pos.x = floor( random( 1, wid - 1 ) );
this.pos.y = floor( random( 1, hei - 1 ) );
this.fruitTime = false;
}
}
function setup() {
createCanvas( block * wid, block * hei );
noStroke(); frameRate( frameR );
snake = new Snake();fruit = new Fruit();
}
function keyPressed() {
switch( keyCode ) {
case LEFT_ARROW: snake.dir = L; break;
case RIGHT_ARROW: snake.dir = R; break;
case UP_ARROW: snake.dir = U; break;
case DOWN_ARROW: snake.dir = D;
}
}
function draw() {
background( color( 0, 0x22, 0 ) );
fill( 20, 50, 120 );
for( var i = 0; i < wid; i++ ) {
rect( i * block, 0, block, block );
rect( i * block, height - block, block, block );
}
for( var i = 1; i < hei - 1; i++ ) {
rect( 1, i * block, block, block );
rect( width - block, i * block, block, block );
}
if( fruit.fruitTime ) {
fruit.setFruit();
frameR += .2;
frameRate( frameR );
}
fruit.draw();
snake.update();
if( snake.eat( fruit.pos ) ) {
fruit.fruitTime = true;
}
snake.draw();
fill( 200 );
textStyle( BOLD ); textAlign( RIGHT ); textSize( 120 );
text( ""+( snake.length - 1 ), 690, 440 );
if( !snake.alive ) text( "THE END", 630, 250 );
}
 

Haskell[edit]

{-# LANGUAGE TemplateHaskell #-}
import Control.Monad.Random (getRandomRs)
import Graphics.Gloss.Interface.Pure.Game
import Lens.Micro ((%~), (^.), (&), set)
import Lens.Micro.TH (makeLenses)
 
--------------------------------------------------------------------------------
-- all data types
 
data Snake = Snake { _body :: [Point], _direction :: Point }
makeLenses ''Snake
 
data World = World { _snake :: Snake , _food :: [Point]
, _score :: Int , _maxScore :: Int }
makeLenses ''World
 
--------------------------------------------------------------------------------
-- everything snake can do
 
moves (Snake b d) = Snake (step b d : init b) d
eats (Snake b d) = Snake (step b d : b) d
bites (Snake b _) = any (== head b)
step ((x,y):_) (a,b) = (x+a, y+b)
 
turn (x',y') (Snake b (x,y)) | (x+x',y+y') == (0,0) = Snake b (x,y)
| otherwise = Snake b (x',y')
 
--------------------------------------------------------------------------------
-- all randomness
 
createWorld = do xs <- map fromIntegral <$> getRandomRs (2, 38 :: Int)
ys <- map fromIntegral <$> getRandomRs (2, 38 :: Int)
return (Ok, World snake (zip xs ys) 0 0)
where
snake = Snake [(20, 20)] (1,0)
 
-------------------------------------------------------------------------------
-- A tyny DSL for declarative description of business logic
 
data Status = Ok | Fail | Stop
 
continue = \x -> (Ok, x)
stop = \x -> (Stop, x)
f >>> g = \x -> case f x of { (Ok, y) -> g y; b -> b } -- chain composition
f <|> g = \x -> case f x of { (Fail, _) -> g x; b -> b } -- alternative
p ==> f = \x -> if p x then f x else (Fail, x) -- condition
l .& f = continue . (l %~ f) -- modification
l .= y = continue . set l y -- setting
 
--------------------------------------------------------------------------------
-- all business logic
 
updateWorld _ = id >>> (snakeEats <|> snakeMoves)
where
snakeEats = (snakeFindsFood ==> (snake .& eats)) >>>
(score .& (+1)) >>> (food .& tail)
 
snakeMoves = (snakeBitesTail ==> stop) <|>
(snakeHitsWall ==> stop) <|>
(snake .& moves)
 
snakeFindsFood w = (w^.snake & moves) `bites` (w^.food & take 1)
snakeBitesTail w = (w^.snake) `bites` (w^.snake.body & tail)
snakeHitsWall w = (w^.snake.body) & head & isOutside
isOutside (x,y) = or [x <= 0, 40 <= x, y <= 0, 40 <= y]
 
--------------------------------------------------------------------------------
-- all event handing
 
handleEvents e (s,w) = f w
where f = case s of
Ok -> case e of
EventKey (SpecialKey k) _ _ _ -> case k of
KeyRight -> snake .& turn (1,0)
KeyLeft -> snake .& turn (-1,0)
KeyUp -> snake .& turn (0,1)
KeyDown -> snake .& turn (0,-1)
_-> continue
_-> continue
_-> \w -> w & ((snake.body) .= [(20,20)]) >>>
(maxScore .& max (w^.score)) >>> (score .= 0)
 
--------------------------------------------------------------------------------
-- all graphics
 
renderWorld (s, w) = pictures [frame, color c drawSnake, drawFood, showScore]
where c = case s of { Ok -> orange; _-> red }
drawSnake = foldMap (rectangleSolid 10 10 `at`) (w^.snake.body)
drawFood = color blue $ circleSolid 5 `at` (w^.food & head)
frame = color black $ rectangleWire 400 400
showScore = color orange $ scale 0.2 0.2 $ txt `at` (-80,130)
txt = Text $ mconcat ["Score: ", w^.score & show
," Maximal score: ", w^.maxScore & show]
at p (x,y) = Translate (10*x-200) (10*y-200) p
 
--------------------------------------------------------------------------------
 
main = do world <- createWorld
play inW white 7 world renderWorld handleEvents updateWorld
where inW = InWindow "The Snake" (400, 400) (10, 10)

Extra credit

It is easy to make snake to seek food automatically. Just change the first line of the updateWorld definition:

updateWorld _ =  id >>> snakeSeeksFood >>> (snakeEats <|> snakeMoves) 

and add local definition:

    snakeSeeksFood w = w & snake .& turns optimalDirection
where
optimalDirection = minimumBy (comparing distanceToFood) safeTurns
 
safeTurns = filter safe [(x,y),(-y,x),(y,-x)] `ifEmpty` [(x,y)]
where (x,y) = w^.snake.direction
safe d = let w'' = w & snake %~ moves . turns d
in not (snakeBitesTail w'' || snakeHitsWall w'')
lst `ifEmpty` x = if null lst then x else lst
 
distanceToFood d = let (a,b) = w^.snake & turns d & moves & (^.body) & head
(x,y) = w^.food & head
in (a-x)^2 + (b-y)^2

Perl[edit]

Snake game perl.png
use utf8;
use Time::HiRes qw(sleep);
use Term::ANSIColor qw(colored);
use Term::ReadKey qw(ReadMode ReadLine);
 
binmode(STDOUT, ':utf8');
 
use constant {
VOID => 0,
HEAD => 1,
BODY => 2,
TAIL => 3,
FOOD => 4,
};
 
use constant {
LEFT => [+0, -1],
RIGHT => [+0, +1],
UP => [-1, +0],
DOWN => [+1, +0],
};
 
use constant {
BG_COLOR => "on_black",
SLEEP_SEC => 0.05,
};
 
use constant {
SNAKE_COLOR => ('bold green' . ' ' . BG_COLOR),
FOOD_COLOR => ('red' . ' ' . BG_COLOR),
};
 
use constant {
U_HEAD => colored('▲', SNAKE_COLOR),
D_HEAD => colored('▼', SNAKE_COLOR),
L_HEAD => colored('◀', SNAKE_COLOR),
R_HEAD => colored('▶', SNAKE_COLOR),
 
U_BODY => colored('╹', SNAKE_COLOR),
D_BODY => colored('╻', SNAKE_COLOR),
L_BODY => colored('╴', SNAKE_COLOR),
R_BODY => colored('╶', SNAKE_COLOR),
 
U_TAIL => colored('╽', SNAKE_COLOR),
D_TAIL => colored('╿', SNAKE_COLOR),
L_TAIL => colored('╼', SNAKE_COLOR),
R_TAIL => colored('╾', SNAKE_COLOR),
 
A_VOID => colored(' ', BG_COLOR),
A_FOOD => colored('❇', FOOD_COLOR),
};
 
local $| = 1;
 
my $w = eval { `tput cols` } || 80;
my $h = eval { `tput lines` } || 24;
my $r = "\033[H";
 
my @grid = map {
[map { [VOID] } 1 .. $w]
} 1 .. $h;
 
my $dir = LEFT;
my @head_pos = ($h / 2, $w / 2);
my @tail_pos = ($head_pos[0], $head_pos[1] + 1);
 
$grid[$head_pos[0]][$head_pos[1]] = [HEAD, $dir]; # head
$grid[$tail_pos[0]][$tail_pos[1]] = [TAIL, $dir]; # tail
 
sub create_food {
my ($food_x, $food_y);
 
do {
$food_x = rand($w);
$food_y = rand($h);
} while ($grid[$food_y][$food_x][0] != VOID);
 
$grid[$food_y][$food_x][0] = FOOD;
}
 
create_food();
 
sub display {
my $i = 0;
 
print $r, join("\n",
map {
join("",
map {
my $t = $_->[0];
if ($t != FOOD and $t != VOID) {
my $p = $_->[1];
$i =
$p eq UP ? 0
: $p eq DOWN ? 1
: $p eq LEFT ? 2
: 3;
}
$t == HEAD ? (U_HEAD, D_HEAD, L_HEAD, R_HEAD)[$i]
: $t == BODY ? (U_BODY, D_BODY, L_BODY, R_BODY)[$i]
: $t == TAIL ? (U_TAIL, D_TAIL, L_TAIL, R_TAIL)[$i]
: $t == FOOD ? (A_FOOD)
: (A_VOID);
 
} @{$_}
)
} @grid
);
}
 
sub move {
my $grew = 0;
 
# Move the head
{
my ($y, $x) = @head_pos;
 
my $new_y = ($y + $dir->[0]) % $h;
my $new_x = ($x + $dir->[1]) % $w;
 
my $cell = $grid[$new_y][$new_x];
my $t = $cell->[0];
 
if ($t == BODY or $t == TAIL) {
die "Game over!\n";
}
elsif ($t == FOOD) {
create_food();
$grew = 1;
}
 
# Create a new head
$grid[$new_y][$new_x] = [HEAD, $dir];
 
# Replace the current head with body
$grid[$y][$x] = [BODY, $dir];
 
# Save the position of the head
@head_pos = ($new_y, $new_x);
}
 
# Move the tail
if (not $grew) {
my ($y, $x) = @tail_pos;
 
my $pos = $grid[$y][$x][1];
my $new_y = ($y + $pos->[0]) % $h;
my $new_x = ($x + $pos->[1]) % $w;
 
$grid[$y][$x][0] = VOID; # erase the current tail
$grid[$new_y][$new_x][0] = TAIL; # create a new tail
 
# Save the position of the tail
@tail_pos = ($new_y, $new_x);
}
}
 
ReadMode(3);
while (1) {
my $key;
until (defined($key = ReadLine(-1))) {
move();
display();
sleep(SLEEP_SEC);
}
 
if ($key eq "\e[A" and $dir ne DOWN ) { $dir = UP }
elsif ($key eq "\e[B" and $dir ne UP ) { $dir = DOWN }
elsif ($key eq "\e[C" and $dir ne LEFT ) { $dir = RIGHT }
elsif ($key eq "\e[D" and $dir ne RIGHT) { $dir = LEFT }
}

Perl 6[edit]

Works with: Rakudo version 2016.08

This is a variation of a demo script included in the examples folder for the Perl 6 SDL2::Raw library bindings.

use SDL2::Raw;
use Cairo;
 
constant W = 1280;
constant H = 960;
 
constant FIELDW = W div 32;
constant FIELDH = H div 32;
 
SDL_Init(VIDEO);
 
my $window = SDL_CreateWindow(
'Snake',
SDL_WINDOWPOS_CENTERED_MASK,
SDL_WINDOWPOS_CENTERED_MASK,
W, H,
OPENGL
);
 
my $render = SDL_CreateRenderer($window, -1, ACCELERATED +| PRESENTVSYNC);
 
my $snake_image = Cairo::Image.record(
-> $_ {
.save;
.rectangle: 0, 0, 64, 64;
.clip;
.rgb: 0, 1, 0;
.rectangle: 0, 0, 64, 64;
.fill :preserve;
.rgb: 0, 0, 0;
.stroke;
.restore;
 
.save;
.translate: 64, 0;
.rectangle: 0, 0, 64, 64;
.clip;
.rgb: 1, 0, 0;
.arc: 32, 32, 30, 0, 2 * pi;
.fill :preserve;
.rgb: 0, 0, 0;
.stroke;
.restore;
}, 128, 128, Cairo::FORMAT_ARGB32);
 
my $snake_texture = SDL_CreateTexture(
$render,
%PIXELFORMAT<ARGB8888>,
STATIC,
128,
128
);
 
SDL_UpdateTexture(
$snake_texture,
SDL_Rect.new(
:x(0),
:y(0),
:w(128),
:h(128)
),
$snake_image.data,
$snake_image.stride // 128 * 4
);
 
SDL_SetTextureBlendMode($snake_texture, 1);
 
SDL_SetRenderDrawBlendMode($render, 1);
 
my $snakepiece_srcrect = SDL_Rect.new(:w(64), :h(64));
my $nompiece_srcrect = SDL_Rect.new(:w(64), :h(64), :x(64));
 
my $event = SDL_Event.new;
 
enum GAME_KEYS (
K_UP => 82,
K_DOWN => 81,
K_LEFT => 80,
K_RIGHT => 79,
);
 
my Complex @snakepieces = 10+10i;
my Complex @noms;
my Complex $snakedir = 1+0i;
my $nomspawn = 0;
my $snakespeed = 0.1;
my $snakestep = 0;
my $nom = 4;
 
my $last_frame_start = now;
main: loop {
my $start = now;
my $dt = $start - $last_frame_start // 0.00001;
while SDL_PollEvent($event) {
my $casted_event = SDL_CastEvent($event);
given $casted_event {
when *.type == QUIT { last main }
when *.type == KEYDOWN {
if GAME_KEYS(.scancode) -> $comm {
given $comm {
when 'K_LEFT' { $snakedir = -1+0i unless $snakedir == 1+0i }
when 'K_RIGHT' { $snakedir = 1+0i unless $snakedir == -1+0i }
when 'K_UP' { $snakedir = 0-1i unless $snakedir == 0+1i }
when 'K_DOWN' { $snakedir = 0+1i unless $snakedir == 0-1i }
}
}
}
}
}
 
if ($nomspawn -= $dt) < 0 {
$nomspawn += 1;
@noms.push: (^FIELDW).pick + (^FIELDH).pick * i unless @noms > 3;
@noms.pop if @noms[*-1] == any(@snakepieces);
}
 
if ($snakestep -= $dt) < 0 {
$snakestep += $snakespeed;
 
@snakepieces.unshift: do given @snakepieces[0] {
($_.re + $snakedir.re) % FIELDW
+ (($_.im + $snakedir.im) % FIELDH) * i
}
 
if @snakepieces[2..*].first( * == @snakepieces[0], :k ) -> $idx {
@snakepieces = @snakepieces[0..($idx + 1)];
}
 
@noms .= grep(
{ $^piece == @snakepieces[0] ?? ($nom += 1) && False !! True }
);
 
if $nom == 0 {
@snakepieces.pop;
} else {
$nom = $nom - 1;
}
}
 
for @snakepieces {
SDL_SetTextureColorMod(
$snake_texture,
255,
(cos((++$) / 2) * 100 + 155).round,
255
);
 
SDL_RenderCopy(
$render,
$snake_texture,
$snakepiece_srcrect,
SDL_Rect.new(.re * 32, .im * 32, 32, 32)
);
}
 
SDL_SetTextureColorMod($snake_texture, 255, 255, 255);
 
for @noms {
SDL_RenderCopy(
$render,
$snake_texture,
$nompiece_srcrect,
SDL_Rect.new(.re * 32, .im * 32, 32, 32)
)
}
 
SDL_RenderPresent($render);
SDL_SetRenderDrawColor($render, 0, 0, 0, 0);
SDL_RenderClear($render);
 
$last_frame_start = $start;
sleep(1 / 50);
}
 
SDL_Quit();

Sidef[edit]

class SnakeGame(w, h) {
const readkey = frequire('Term::ReadKey')
const ansi = frequire('Term::ANSIColor')
 
enum (VOID, HEAD, BODY, TAIL, FOOD)
 
define (
LEFT = [+0, -1],
RIGHT = [+0, +1],
UP = [-1, +0],
DOWN = [+1, +0],
)
 
define BG_COLOR = "on_black"
define FOOD_COLOR = ("red" + " " + BG_COLOR)
define SNAKE_COLOR = ("bold green" + " " + BG_COLOR)
define SLEEP_SEC = 0.02
 
const (
A_VOID = ansi.colored(' ', BG_COLOR),
A_FOOD = ansi.colored('❇', FOOD_COLOR),
A_BLOCK = ansi.colored('■', SNAKE_COLOR),
)
 
has dir = LEFT
has grid = [[]]
has head_pos = [0, 0]
has tail_pos = [0, 0]
 
method init {
grid = h.of { w.of { [VOID] } }
 
head_pos = [h//2, w//2]
tail_pos = [head_pos[0], head_pos[1]+1]
 
grid[head_pos[0]][head_pos[1]] = [HEAD, dir] # head
grid[tail_pos[0]][tail_pos[1]] = [TAIL, dir] # tail
 
self.make_food()
}
 
method make_food {
var (food_x, food_y)
 
do {
food_x = w.rand.int
food_y = h.rand.int
} while (grid[food_y][food_x][0] != VOID)
 
grid[food_y][food_x][0] = FOOD
}
 
method display {
print("\033[H", grid.map { |row|
row.map { |cell|
given (cell[0]) {
when (VOID) { A_VOID }
when (FOOD) { A_FOOD }
default { A_BLOCK }
}
}.join('')
}.join("\n")
)
}
 
method move {
var grew = false
 
# Move the head
var (y, x) = head_pos...
 
var new_y = (y+dir[0] % h)
var new_x = (x+dir[1] % w)
 
var cell = grid[new_y][new_x]
 
given (cell[0]) {
when (BODY) { die "\nYou just bit your own body!\n" }
when (TAIL) { die "\nYou just bit your own tail!\n" }
when (FOOD) { grew = true; self.make_food() }
}
 
# Create a new head
grid[new_y][new_x] = [HEAD, dir]
 
# Replace the current head with body
grid[y][x] = [BODY, dir]
 
# Update the head position
head_pos = [new_y, new_x]
 
# Move the tail
if (!grew) {
var (y, x) = tail_pos...
 
var pos = grid[y][x][1]
var new_y = (y+pos[0] % h)
var new_x = (x+pos[1] % w)
 
grid[y][x][0] = VOID # erase the current tail
grid[new_y][new_x][0] = TAIL # create a new tail
 
tail_pos = [new_y, new_x]
}
}
 
method play {
STDOUT.autoflush(true)
readkey.ReadMode(3)
 
try {
loop {
var key
while (!defined(key = readkey.ReadLine(-1))) {
self.move()
self.display()
Sys.sleep(SLEEP_SEC)
}
 
given (key) {
when ("\e[A") { if (dir != DOWN ) { dir = UP } }
when ("\e[B") { if (dir != UP ) { dir = DOWN } }
when ("\e[C") { if (dir != LEFT ) { dir = RIGHT } }
when ("\e[D") { if (dir != RIGHT) { dir = LEFT } }
}
}
}
catch {
readkey.ReadMode(0)
}
}
}
 
var w = `tput cols`.to_i
var h = `tput lines`.to_i
 
SnakeGame(w || 80, h || 24).play