Змейка на javascript

https://github.com/koneshno-vasya/snake https://snake--vasya228.repl.co/ Игра простая. Буду благодарен за критику

let canvas = document.getElementById("canvas");        
let ctx = canvas.getContext("2d");
let h = window.screen.availHeight;
let w = window.screen.availWidth;
let fieldNumberOfCells = 20;
let cellSize;
let gameField = [];
let direction = 1;//0 - west, 1 south 2 east 3 north
let snakeTail = [[10,6],[9,6],[8,6]]; //snakeTail[index of part][x/y of this part]
let r;
let score = 0;
let highscore = document.cookie;
let foodCell;
let timer;
let isItAPc = 0;
let attempts = 0;
let alreadyScreamed = 0;
let speed = 200;
addEventListener("keydown", rotate);

let up1 = document.getElementById("up");
up1.onclick = function(e){
    if(direction!=1){  
        direction = 3;
    }
};
let down1 = document.getElementById("down");
down1.onclick = function(e){
    if(direction!=3){  
        direction = 1;
    }
};
let left1 = document.getElementById("left");
left1.onclick = function(e){
    if(direction!=0){  
        direction = 2;
    }
};
let right1 = document.getElementById("right");
right1.onclick = function(e){
    if(direction!=2){  
        direction = 0;
    }
};

if (h>w){ //mobile
    document.getElementsByClassName('wrap')[0].style.width = w+"px";
    document.getElementsByClassName('wrap')[0].style.height = Math.round((h-w)/2-50)+"px";
    canvas.setAttribute("height",w);
    canvas.setAttribute("width",w);
    cellSize = Math.round(w/fieldNumberOfCells);        
}

if (h<=w){ //pc
    h = h-h/3;
    canvas.setAttribute("height",h);
    canvas.setAttribute("width",h);
    document.getElementById("wrap").innerHTML = "";//для пк кнопки не нужны
    isItAPc=1;
    cellSize = Math.round((h)/fieldNumberOfCells);
}
launch();
function launch(){
    score=0;
    direction = 1;
    foodCell = [Math.floor(Math.random() * fieldNumberOfCells),Math.floor(Math.random() * fieldNumberOfCells)];
    snakeTail = [[10,6],[9,6],[8,6]];
    for (var i = 0; i < fieldNumberOfCells; i++){
    gameField[i] = [];
    for (var i2 = 0; i2 < fieldNumberOfCells; i2++){
        gameField[i][i2] = 0;//gameField initialisation
        }
    }
    timer = setInterval(main,speed);
}
// init end 
function main(){
    move();
    draw();
}
function rotate(e){
    if (r == 0){ // не позволяет сменить направление более чем один раз за цикл
        if(e.keyCode == 37 && direction!=0){  
            direction = 2;
        }
        if(e.keyCode == 38 && direction!=1){  
            direction = 3;
        }
        if(e.keyCode == 39 && direction!=2){  
            direction = 0;
        }
        if(e.keyCode == 40 && direction!=3){  
            direction = 1;
        }
        r = 1;
    }

}
function move(){
    let snakeTailCopy = snakeTail;
    snakeTailCopy = snakeTailCopy.slice();
    collisionCheck();
    if(direction==0){
        snakeTail[0] = [snakeTail[0][0]+1,snakeTail[0][1]];
    }
    if(direction==1){
        snakeTail[0] = [snakeTail[0][0],snakeTail[0][1]+1];
    }
    if(direction==2){
        snakeTail[0] = [snakeTail[0][0]-1,snakeTail[0][1]];
    }
    if(direction==3){
        snakeTail[0] = [snakeTail[0][0],snakeTail[0][1]-1];
    }
    for(let i = 1;i < snakeTail.length; i++){
        snakeTail[i] = snakeTailCopy[i-1];
    }
    for (let i = 0; i < snakeTail.length; i++){// move invisible snaketail array to visible gameField array
        if (snakeTail[0][0] < gameField[0].length && snakeTail[0][0] >= 0){//защита от обращений к необьявленным элементам массива
            gameField[snakeTail[i][0]][snakeTail[i][1]] = 1;
        }
    }
    if(snakeTail[0][0] == foodCell[0] && snakeTail[0][1] == foodCell[1]){// eat food, increase snake leight
        snakeTail[snakeTail.length] = snakeTailCopy[snakeTailCopy.length - 1];
        score++;
        foodCell = [Math.floor(Math.random() * fieldNumberOfCells),Math.floor(Math.random() * fieldNumberOfCells)];

    }else{
    gameField[snakeTailCopy[snakeTailCopy.length-1] [0]]   [snakeTailCopy[snakeTailCopy.length-1] [1]] = 0;
    }
    r = 0;
}

function collisionCheck(){
    //collision with walls
    if(direction==0 && snakeTail[0][0] + 1 == fieldNumberOfCells){
        gameover();
    }
    if(direction==1 && snakeTail[0][1] + 1 == fieldNumberOfCells){
        gameover();
    }
    if(direction==2 && snakeTail[0][0] - 1 == -1){
        gameover();
    }
    if(direction==3 && snakeTail[0][1] - 1 == -1){
        gameover();
    }
    //collision with tail
    for(let i = 1;i < snakeTail.length; i++){
        if(direction==0 && snakeTail[0][0] + 1 == snakeTail[i][0] && snakeTail[0][1] == snakeTail[i][1]){
        gameover();
        }
        if(direction==1 && snakeTail[0][1] + 1 == snakeTail[i][1] && snakeTail[0][0] == snakeTail[i][0]){
            gameover();
        }
        if(direction==2 && snakeTail[0][0] - 1 == snakeTail[i][0] && snakeTail[0][1] == snakeTail[i][1]){
            gameover();
        }
        if(direction==3 && snakeTail[0][1] - 1 == snakeTail[i][1] && snakeTail[0][0] == snakeTail[i][0]){
            gameover();
        }
    }
}
function gameover(){
    clearInterval(timer);
    if(score > highscore){
        highscore = score;
        document.cookie = highscore;
    }
    if (isItAPc == 1 && score>6){
        screamer();
    }else{
        timer = setTimeout(launch,1000);
    }
}
function screamer(){
        document.getElementById("prikol").innerHTML = "<img id=\"img\" src=\"/blue-screen-png-7.png\">";        
        document.getElementById("img").requestFullscreen();         
}

function draw(){
    ctx.fillStyle = "black";
    ctx.fillRect(0, 0, h, w);
    for(let i = 0; i < fieldNumberOfCells; i++){
        for(let i2 = 0; i2<fieldNumberOfCells; i2++){
            if (gameField[i][i2] == 1){// draw snake
                ctx.fillStyle = "white";
                ctx.fillRect(i*cellSize, i2*cellSize, cellSize, cellSize);
            }

            ctx.fillStyle = "blue";// draw food
            ctx.fillRect(cellSize*foodCell[0], cellSize*foodCell[1], cellSize, cellSize);

            document.getElementById("score").innerHTML = score+"  |  HI "+highscore;

        }
    }
}