How do I try to line up the snake and Apple properly in my snake game

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Hello! I am currently working on my personal JavaScript snake game project. I have a snake and apple on the screen right now. I have not yet added the border collision. Right now, I don't know how to force the snake to line up exactly with the apple (the snake and apple can touch even when not aligned properly).

What I have tried:

I have mainly tried checking if the x and y positions are a multiple of my snake width and height before letting the snake move. At the same time for the apple, I tried to find the nearest coordinate point from my random point that would be a multiple of the snake width and height. However, that didn't seem to work, so I deleted that code and I am back on square one. My code below is what I have. Any help is greatly appreciated, and let me know if you need any clarification!

HTML

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Snake Game</title>
    <link rel="stylesheet" href="snake.css">
</head>
<body>
    <canvas id="canvas"></canvas>
    <script src="snake.js"></script>
</body>
</html>

CSS

#canvas {
    position: absolute;
    background-color: black;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
}

JavaScript

 const canvas = document.querySelector('#canvas');
const ctx = canvas.getContext("2d");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
const snakeWidth = 20;
const snakeHeight = 20;
let snakeX = canvas.width / 2;
let snakeY = canvas.height / 2;
let speedX = 0;
let speedY = 0;
const snakeSpeed = 1;
const snakeArray = [];
let prevKey = '';
const posHistory = [];
const canvasArea = canvas.width * canvas.height;
let randX = Math.random() * canvas.width;
let randY = Math.random() * canvas.height;
console.log(snakeX);
console.log(snakeY);

// Makes sure canvas doesn't get distorted
canvas.addEventListener("resize", () => {
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    snakeArray[0].draw();
    apple.drawApple();
});

// Snake 
class Snake {
    constructor() {
        this.width = snakeWidth;
        this.height = snakeHeight;
        this.x = snakeX - (this.width / 2);
        this.y = snakeY - (this.height / 2);
        this.speedX = speedX;
        this.speedY = speedY;
    }

    updateHead() {
        posHistory.push([this.x, this.y]);
        this.x += speedX;
        this.y += speedY;

        if (posHistory.length >= canvasArea)
            posHistory.pop();
    }

    updateTail(index) {
        this.x = posHistory[posHistory.length - index][0];
        this.y = posHistory[posHistory.length - index][1];
    }

    draw() {
        ctx.fillStyle = 'green';
        ctx.fillRect(this.x, this.y, this.width, this.height);
    }
}
snakeArray.push(new Snake());

class Apple {
    constructor() {
        this.width = snakeWidth;
        this.height = snakeHeight;
        this.x = randX - (randX % this.width);
        this.y = randY - (randY % this.height);
    }

    drawApple() {
        ctx.fillStyle = 'red';
        ctx.fillRect(this.x, this.y, this.width, this.height);
    }

    appleCollision() {
        for (let i = 0; i < snakeArray.length; i++) {
            if (Math.abs(this.x - snakeArray[i].x) <= 20 && Math.abs(this.y - snakeArray[i].y) <= 20) {
                addSnake();
                randX = Math.random() * canvas.width;
                randY = Math.random() * canvas.height;
                this.x = randX;
                this.y = randY;
                console.log(this.x, this.y);
;            }
        }
    }
}
const apple = new Apple(); 

// Controls snake
document.addEventListener("keydown", (event) => {
    switch (event.key) {
        case 'ArrowUp': 
            // If not going down
            if (prevKey !== 'down') {
                speedX = 0;
                speedY = -1 * snakeSpeed;
                prevKey = 'up';
            }
            break;
        case 'ArrowRight':
            // If not going left
            if (prevKey !== 'left') {
                speedX = snakeSpeed;
                speedY = 0;
                prevKey = 'right';
            }
            break;
        case 'ArrowDown':
            // If not going up
            if (prevKey !== 'up') {
                speedX = 0;
                speedY = snakeSpeed;
                prevKey = 'down';
            }
            break;
        case 'ArrowLeft':
            // If not going right
            if (prevKey !== 'right') {
                speedX = -1 * snakeSpeed;
                speedY = 0; 
                prevKey = 'left';
            }
            break;   
    }
});

function handleSnake() {   
    snakeArray[0].updateHead();
    for (let i = 1; i < snakeArray.length; i++) {
        snakeArray[i].updateTail(i);
    }

    for (let j = 0; j < snakeArray.length; j++) {
        snakeArray[j].draw();
    }
}

function handleApple() {
    apple.appleCollision();
    apple.drawApple();
}

function addSnake() {
    for (let i = 0; i < Math.round(snakeWidth / snakeSpeed); i++)
        snakeArray.push(new Snake());
}

function animate() {
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    handleSnake();
    handleApple();
    requestAnimationFrame(animate);
}
animate();

Posted 1-May-23 19:48pm

Yash64

Updated 11-Jul-23 19:44pm

v2

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Comments

Member 15627495 2-May-23 2:47am

Hello !

why the snake have an X speed, and a Y speed too, what is the difference ?

one advice :
try to integrate the Canvas as it's a class, like the class snake and Apple ...
because you can launch 'refresh' / apply 'position' on elements on it.
It's to go further with OOP and code structure.

the question is : Are the 'snake and apple' parts of the canvas, or the canvas is part of 'the snake and apple' ?
you can implement a function Canvas..apply_location(target , X, Y , history_pos ) ;

It's to keep Graphics ( the canvas ) out of the class 'Apple' and 'Snake'

Yash64 3-May-23 9:12am

I separated the x and y speeds because they control how the snake moves, and if I have just one speed variable, I don't know how I could alternate between the two so that the snake moves properly. As for the advice, I tried to implement it but failed miserably. Could you show me how to do it please because I am stumped on how to convert canvas to a class. I will continue to try and figure out how to get the apple and snake to line up. I appreciate the help.

[no name] 2-May-23 11:57am

Compute a center point for all your objects (usually left, top + offsets). Then you can compare their relative distances; factoring in the (half) height, (half) width or radius of the objects when necessary.

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Yash64 · Accepted Answer · 2023-05-09T03:08:00

I got the snake to line up mostly. I added a blocksize variable and updated the snake's position by a block. I also used the following equations for the apple: