JSFiddle - React, Tailwind, and code Playground

HTML

<canvas id="enemy" width="800" height="500"></canvas>

CSS

#enemy
{
    background:black;
    border:1px solid white;
}

JavaScript

var enemyCtx = document.getElementById('enemy').getContext('2d');

var game =
{
    w: 800,
    h: 500
};
var enemies = [];
window.addEventListener('load', function()
{
    for (var i = 0; i < 200; i++)
    {
        enemies[enemies.length] = new Enemy();
    }
    update();
}, false);

var buffer = document.createElement('canvas');
    buffer.width = 42;
    buffer.height = 42;
    var bufferCtx = buffer.getContext('2d');
    drawEnemy(bufferCtx, 5, 5, 32, 32, 'red');

function update()
{
    for (var i = 0; i < enemies.length; i++)
    {
                    enemyCtx.clearRect(    enemies[i].x,
                                enemies[i].y,
                                enemies[i].x + enemies[i].width,
                                enemies[i].y + enemies[i].height);
    }
    for (var i = 0; i < enemies.length; i++)
    {
        enemies[i].x-=5;
        enemyCtx.drawImage(buffer, enemies[i].x-5, enemies[i].y-5);
    }
    requestAnimationFrame(update);
}

function drawEnemy(ctx, x, y, width, height, colour)
{
        ctx.lineWidth = 1;
        ctx.strokeStyle = colour;
        ctx.strokeRect(x + 0.5, y + 0.5, width, height);
}

function Enemy()
{
    this.x = Math.random()*game.w;
    this.y = Math.random()*game.h;
    this.width = 32;
    this.height = 32;
}
(function()
{
    // http://paulirish.com/2011/requestanimationframe-for-smart-animating/
    var lastTime = 0;
    var vendors = ['ms', 'moz', 'webkit', 'o'];
    for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x)
    {
        window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame'];
        window.cancelAnimationFrame = window[vendors[x]+'CancelAnimationFrame'] || window[vendors[x]+'CancelRequestAnimationFrame'];
    }

    if (!window.requestAnimationFrame) window.requestAnimationFrame = function(callback, element)
    {
        var currTime = new Date().getTime();
        var timeToCall = Math.max(0, 16 - (currTime - lastTime));
        var id =...