---
title: "Snake Part 3: Movement and Screen Wrapping"
description: "Demonstrates grid-based snake movement with input validation to prevent 180-degree turns, screen wrapping via Phaser.Math.Wrap, and body segment tracking using Phaser.Actions.ShiftPosition."
phaser: "4.1.0"
size: "640x480"
files: 1
url: https://phaser.io/oss/examples/v4.1.0/games/snake/view/part3
site: Phaser - https://phaser.io
---

> This page is about the open-source Phaser framework, for writing a game's code by hand. To make a game with AI, use Phaser AE (https://phaser.io/): the desk's tools work with Web MCP, and the CLI works with your own coding agent. See "For AI agents: Phaser AE" at the end of this page.

# Snake Part 3: Movement and Screen Wrapping

Demonstrates grid-based snake movement with input validation to prevent 180-degree turns, screen wrapping via Phaser.Math.Wrap, and body segment tracking using Phaser.Actions.ShiftPosition.

A Phaser 4.1.0 example in [Games / Snake](https://phaser.io/oss/examples/v4.1.0/games/snake.md). It runs at 640 × 480, and loads its assets from https://cdn.phaserfiles.com/v410. See it running, with its code, at https://phaser.io/oss/examples/v4.1.0/games/snake/view/part3.

To run it, load Phaser 4.1.0 (`https://cdn.jsdelivr.net/npm/phaser@4.1.0/dist/phaser.min.js`), then the file, on a page with a `<div id="game-container">`.

## Code

### part3.js

```js
var config = {
    scale: { mode: Phaser.Scale.FIT },
    type: Phaser.WEBGL,
    width: 640,
    height: 480,
    backgroundColor: '#bfcc00',
    parent: 'game-container',
    scene: {
        preload: preload,
        create: create,
        update: update
    }
};

var snake;
var food;
var cursors;

//  Direction consts
var UP = 0;
var DOWN = 1;
var LEFT = 2;
var RIGHT = 3;

var game = new Phaser.Game(config);

function preload ()
{
        this.load.setBaseURL('https://cdn.phaserfiles.com/v410');
    this.load.image('food', 'assets/games/snake/food.png');
    this.load.image('body', 'assets/games/snake/body.png');
}

function create ()
{
    var Food = new Phaser.Class({

        Extends: Phaser.GameObjects.Image,

        initialize:

        function Food (scene, x, y)
        {
            Phaser.GameObjects.Image.call(this, scene)

            this.setTexture('food');
            this.setPosition(x * 16, y * 16);
            this.setOrigin(0);

            this.total = 0;

            scene.children.add(this);
        }

    });

    var Snake = new Phaser.Class({

        initialize:

        function Snake (scene, x, y)
        {
            this.headPosition = new Phaser.Math.Vector2(x, y);

            this.body = scene.add.group();

            this.head = this.body.create(x * 16, y * 16, 'body');
            this.head.setOrigin(0);

            this.alive = true;

            this.speed = 100;

            this.moveTime = 0;

            this.tail = new Phaser.Math.Vector2(x, y);

            this.heading = RIGHT;
            this.direction = RIGHT;
        },

        update: function (time)
        {
            if (time >= this.moveTime)
            {
                return this.move(time);
            }
        },

        faceLeft: function ()
        {
            if (this.direction === UP || this.direction === DOWN)
            {
                this.heading = LEFT;
            }
        },

        faceRight: function ()
        {
            if (this.direction === UP || this.direction === DOWN)
            {
                this.heading = RIGHT;
            }
        },

        faceUp: function ()
        {
            if (this.direction === LEFT || this.direction === RIGHT)
            {
                this.heading = UP;
            }
        },

        faceDown: function ()
        {
            if (this.direction === LEFT || this.direction === RIGHT)
            {
                this.heading = DOWN;
            }
        },

        move: function (time)
        {
            /**
            * Based on the heading property (which is the direction the pgroup pressed)
            * we update the headPosition value accordingly.
            * 
            * The Math.wrap call allow the snake to wrap around the screen, so when
            * it goes off any of the sides it re-appears on the other.
            */
            switch (this.heading)
            {
                case LEFT:
                    this.headPosition.x = Phaser.Math.Wrap(this.headPosition.x - 1, 0, 40);
                    break;

                case RIGHT:
                    this.headPosition.x = Phaser.Math.Wrap(this.headPosition.x + 1, 0, 40);
                    break;

                case UP:
                    this.headPosition.y = Phaser.Math.Wrap(this.headPosition.y - 1, 0, 30);
                    break;

                case DOWN:
                    this.headPosition.y = Phaser.Math.Wrap(this.headPosition.y + 1, 0, 30);
                    break;
            }

            this.direction = this.heading;

            //  Update the body segments and place the last coordinate into this.tail
            Phaser.Actions.ShiftPosition(this.body.getChildren(), this.headPosition.x * 16, this.headPosition.y * 16, 1, this.tail);

            //  Update the timer ready for the next movement
            this.moveTime = time + this.speed;

            return true;
        }

    });

    food = new Food(this, 3, 4);

    snake = new Snake(this, 8, 8);

    //  Create our keyboard controls
    cursors = this.input.keyboard.createCursorKeys();
}

function update (time, delta)
{
    if (!snake.alive)
    {
        return;
    }

    /**
    * Check which key is pressed, and then change the direction the snake
    * is heading based on that. The checks ensure you don't double-back
    * on yourself, for example if you're moving to the right and you press
    * the LEFT cursor, it ignores it, because the only valid directions you
    * can move in at that time is up and down.
    */
    if (cursors.left.isDown)
    {
        snake.faceLeft();
    }
    else if (cursors.right.isDown)
    {
        snake.faceRight();
    }
    else if (cursors.up.isDown)
    {
        snake.faceUp();
    }
    else if (cursors.down.isDown)
    {
        snake.faceDown();
    }

    snake.update(time);
}
```

## More in Snake

- [Snake Game - Part 7](https://phaser.io/oss/examples/v4.1.0/games/snake/view/part7.md): A complete Snake game implementation featuring grid-based movement, screen wrapping, body growth, self-collision detection, and a system to spawn food only on unoccupied grid tiles.
- [Snake Game: Growth and Food Spawning](https://phaser.io/oss/examples/v4.1.0/games/snake/view/part6.md): A comprehensive example of a Snake game featuring grid-based movement, body growth using ShiftPosition, and a system to spawn food only in valid empty grid locations.
- [Snake Game: Part 1 - Asset Loading](https://phaser.io/oss/examples/v4.1.0/games/snake/view/part1.md): Initial setup for a Snake game, including game configuration and preloading image assets for the food and snake body.
- [Snake Part 2 - Movement and Wrapping](https://phaser.io/oss/examples/v4.1.0/games/snake/view/part2.md): Implement grid-based movement with timed updates, screen wrapping, and directional controls that prevent reversing direction.
- [Snake Part 4: Growth and Food Collision](https://phaser.io/oss/examples/v4.1.0/games/snake/view/part4.md): Implementation of snake movement with grid-based screen wrapping, food collection, and growing the snake body using group actions.
- [Snake Part 5: Food and Growth](https://phaser.io/oss/examples/v4.1.0/games/snake/view/part5.md): This example demonstrates implementing food consumption and snake growth mechanics, including speed increases and tail management using Phaser.Actions.ShiftPosition.

---

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