الصفحة الرئيسية

html, body {
height: 100%;
margin: 0;
}

body {
background: black;
display: flex;
align-items: center;
justify-content: center;
}
canvas {
border: 1px solid white;
}

var canvas = document.getElementById(‘game’);
var context = canvas.getContext(‘2d’);

var grid = 16;
var count = 0;

var snake = {
x: 160,
y: 160,

// snake velocity. moves one grid length every frame in either the x or y direction
dx: grid,
dy: 0,

// keep track of all grids the snake body occupies
cells: [],

// length of the snake. grows when eating an apple
maxCells: 4
};
var apple = {
x: 320,
y: 320
};

// get random whole numbers in a specific range
// @see https://stackoverflow.com/a/1527820/2124254
function getRandomInt(min, max) {
return Math.floor(Math.random() * (max – min)) + min;
}

// game loop
function loop() {
requestAnimationFrame(loop);

// slow game loop to 15 fps instead of 60 (60/15 = 4)
if (++count < 4) {
return;
}

count = 0;
context.clearRect(0,0,canvas.width,canvas.height);

// move snake by it's velocity
snake.x += snake.dx;
snake.y += snake.dy;

// wrap snake position horizontally on edge of screen
if (snake.x = canvas.width) {
snake.x = 0;
}

// wrap snake position vertically on edge of screen
if (snake.y = canvas.height) {
snake.y = 0;
}

// keep track of where snake has been. front of the array is always the head
snake.cells.unshift({x: snake.x, y: snake.y});

// remove cells as we move away from them
if (snake.cells.length > snake.maxCells) {
snake.cells.pop();
}

// draw apple
context.fillStyle = ‘red’;
context.fillRect(apple.x, apple.y, grid-1, grid-1);

// draw snake one cell at a time
context.fillStyle = ‘green’;
snake.cells.forEach(function(cell, index) {

// drawing 1 px smaller than the grid creates a grid effect in the snake body so you can see how long it is
context.fillRect(cell.x, cell.y, grid-1, grid-1);

// snake ate apple
if (cell.x === apple.x && cell.y === apple.y) {
snake.maxCells++;

// canvas is 400×400 which is 25×25 grids
apple.x = getRandomInt(0, 25) * grid;
apple.y = getRandomInt(0, 25) * grid;
}

// check collision with all cells after this one (modified bubble sort)
for (var i = index + 1; i < snake.cells.length; i++) {

// snake occupies same space as a body part. reset game
if (cell.x === snake.cells[i].x && cell.y === snake.cells[i].y) {
snake.x = 160;
snake.y = 160;
snake.cells = [];
snake.maxCells = 4;
snake.dx = grid;
snake.dy = 0;

apple.x = getRandomInt(0, 25) * grid;
apple.y = getRandomInt(0, 25) * grid;
}
}
});
}

// listen to keyboard events to move the snake
document.addEventListener('keydown', function(e) {
// prevent snake from backtracking on itself by checking that it's
// not already moving on the same axis (pressing left while moving
// left won't do anything, and pressing right while moving left
// shouldn't let you collide with your own body)

// left arrow key
if (e.which === 37 && snake.dx === 0) {
snake.dx = -grid;
snake.dy = 0;
}
// up arrow key
else if (e.which === 38 && snake.dy === 0) {
snake.dy = -grid;
snake.dx = 0;
}
// right arrow key
else if (e.which === 39 && snake.dx === 0) {
snake.dx = grid;
snake.dy = 0;
}
// down arrow key
else if (e.which === 40 && snake.dy === 0) {
snake.dy = grid;
snake.dx = 0;
}
});

// start the game
requestAnimationFrame(loop);