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HTML 

              
                <div class="pong">
	<div class="paddle paddle-player"></div>
	<div class="paddle paddle-enemy"></div>
	<div class="score score-player">0</div>
	<div class="score score-enemy">0</div>
	<div class="net"></div>
	<div class="ball"></div>
</div>
!

CSS 

              
                html,
body {
	height: 100%;	
}

body {
	background: #111;
	background: radial-gradient(#222, #111);
	overflow: hidden;
}

.pong,
.pong * {
	position: absolute;
}

.pong {
	box-shadow: 0 0 0 8px #666;
	height: 1080px;
	left: 50%;
	top: 50%;
	width: 1920px;
}

.paddle {
	background: #fff;
	height: 240px;
	left: 0;
	top: 0;
	width: 60px;
}

.paddle-player { 
	background: hsl(130, 100%, 60%);
}

.paddle-enemy {
	background: hsl(200, 100%, 60%);
}

.score {
	color: white;
	font: bold 6em/1 'Roboto Mono', monospace;
	top: 80px;
}

.score-player {
	color: hsl(130, 100%, 60%);
	left: 180px;
}

.score-enemy {
	color: hsl(200, 100%, 60%);
	right: 180px;
}

.net {
	background: #666;
	height: 100%;
	left: 50%;
	margin-left: -2px;
	top: 0;
	width: 4px;
}

.ball {
	background: #fff;
	height: 60px;
	left: 0;
	top: 0;
	width: 60px;
}
!

JS 

              
                /*==========================================
Config 
==========================================*/

// game
var gameWidth = 1920,
	gameHeight = 1080;

// paddles
var paddleWidth = 60,
	paddleHeight = 240,
	paddleSpeed = 16;

// ball
var ballWidth = 60,
	ballHeight = 60,
	ballSpeedStart = 16,
	ballSpeed = ballSpeedStart;

// score - what are we playing to?
var scoreMax = 5;

/*==========================================
Objects 
==========================================*/

var paddlePlayer = {
	elem: document.querySelector('.paddle-player'),
	x: 0,
	y: gameHeight / 2 - paddleHeight / 2,
	width: paddleWidth,
	height: paddleHeight,
	speed: paddleSpeed,
	moveUp: false,
	moveDown: false
};

var paddleEnemy = {
	elem: document.querySelector('.paddle-enemy'),
	x: gameWidth - paddleWidth,
	y: gameHeight / 2 - paddleHeight / 2,
	width: paddleWidth,
	height: paddleHeight,
	speed: paddleSpeed,
	moveUp: false,
	moveDown: false
};
	
var ball = {
	elem: document.querySelector('.ball'),
	x: gameWidth / 2 - ballWidth / 2,
	y: gameHeight / 2 - ballHeight / 2,
	vx: ballSpeed,
	vy: ballSpeed,
	width: ballWidth,
	height: ballHeight
};

var scorePlayer = {
	elem: document.querySelector('.score-player'),
	value: 0
};

var scoreEnemy = {
	elem: document.querySelector('.score-enemy'),
	value: 0
};

/*==========================================
Initialize 
==========================================*/

function init() {
	addEventListeners();
	loop();
}

/*==========================================
Resets
==========================================*/

function resetGame() {
	ballSpeed = ballSpeedStart;
	scorePlayer.value = 0;
	scoreEnemy.value = 0;
	resetBall();
}

function resetBall() {
	ball.x = gameWidth / 2 - ballWidth / 2;
	ball.y = gameHeight / 2 - ballHeight / 2;
	ball.vx = 0;
	ball.vy = 0;
	setTimeout(function() {
		ball.vx = ballSpeed;
		ball.vy = ballSpeed;
	}, 1000);
}

/*==========================================
Events 
==========================================*/

function addEventListeners() {
	window.addEventListener('keydown', function(e) {
		if (e.which === 38) { 
			paddlePlayer.moveUp = true;
		}
		if (e.which === 40) {
			paddlePlayer.moveDown = true;
		}
	});

	window.addEventListener('keyup', function(e) {
		if (e.which === 38) { 
			paddlePlayer.moveUp = false;
		}
		if (e.which === 40) {
			paddlePlayer.moveDown = false;
		}
	});
}

/*==========================================
AABB Collision Detection
==========================================*/

function collisionAABB(r1, r2) {
	if (!(
		r1.x > r2.x + r2.width ||  // rect1 is on the right of rect2
		r1.x + r1.width < r2.x ||  // rect1 is on the left of rect2
		r1.y > r2.y + r2.height || // rect1 is below rect2
		r1.y + r1.height < r2.y    // rect1 is above rect2
	)) {
		return true;
	}
}

/*==========================================
Move Ball
==========================================*/

function moveBall() {
	ball.x += ball.vx;
	ball.y += ball.vy;
}

/*==========================================
Move Player
==========================================*/

function movePlayer() {
	if (paddlePlayer.moveUp) {
		paddlePlayer.y -= paddlePlayer.speed;
	} else if (paddlePlayer.moveDown) {
		paddlePlayer.y += paddlePlayer.speed;
	}
}

/*==========================================
Move Enemy
==========================================*/

function moveEnemy() {
	if (Math.random() < 0.2) {
		paddleEnemy.moveUp = false;
		paddleEnemy.moveDown = false;
		if (ball.y + ballHeight < paddleEnemy.y + paddleEnemy.height / 2) {
			paddleEnemy.moveUp = true;
		} else if (ball.y > paddleEnemy.y + paddleEnemy.height / 2) {
			paddleEnemy.moveDown = true;
		}
	}
	
	if (paddleEnemy.moveUp) {
		paddleEnemy.y -= paddleEnemy.speed;
	} else if (paddleEnemy.moveDown) {
		paddleEnemy.y += paddleEnemy.speed;
	}
}

/*==========================================
Contain Ball
==========================================*/

function containBall() {
	if (ball.y <= 0) {
		ball.y = 0;
		ball.vy = -ball.vy;
	} else if (ball.y + ball.height >= gameHeight) {
		ball.y = gameHeight - ball.height;
		ball.vy = -ball.vy;
	}

	if (ball.x <= 0) {
		scoreEnemy.value += 1;
		ballSpeed += 1;
		resetBall();
	} else if (ball.x + ball.width >= gameWidth) {
		scorePlayer.value += 1;
		ballSpeed += 1;
		resetBall();
	}
}

/*==========================================
Contain Paddles
==========================================*/

function containPaddles() {
	paddlePlayer.y = Math.max(0, paddlePlayer.y);
	paddlePlayer.y = Math.min(gameHeight - paddlePlayer.height, paddlePlayer.y);
	
	paddleEnemy.y = Math.max(0, paddleEnemy.y);
	paddleEnemy.y = Math.min(gameHeight - paddleEnemy.height, paddleEnemy.y);
}

/*==========================================
Check Collisions
==========================================*/

function checkCollisions() {
	if (collisionAABB(ball, paddlePlayer)) {
		ball.x = paddlePlayer.x + paddlePlayer.width;
		ball.vx = -ball.vx;
	}
	
	if (collisionAABB(ball, paddleEnemy)) {
		ball.x = paddleEnemy.x - ball.width;
		ball.vx = -ball.vx;
	}
}

/*==========================================
Check Win State
==========================================*/

function checkWinState() {
	if (scorePlayer.value >= scoreMax) {
		console.log('You win!');
		resetGame();
	} else if (scoreEnemy.value >= scoreMax) {
		console.log('You get nothing! You lose! Good day, sir!');
		resetGame();
	}
}

/*==========================================
Update
==========================================*/

function update() {
	moveBall();
	movePlayer();
	moveEnemy();
	containBall();
	containPaddles();
	checkCollisions();
	checkWinState();
}

/*==========================================
Render
==========================================*/

function render() {
	paddlePlayer.elem.style.transform = 'translate(' + paddlePlayer.x + 'px, ' + paddlePlayer.y + 'px)';
	paddleEnemy.elem.style.transform = 'translate(' + paddleEnemy.x + 'px, ' + paddleEnemy.y + 'px)';
	ball.elem.style.transform = 'translate(' + ball.x + 'px, ' + ball.y + 'px)';
	scorePlayer.elem.innerHTML = scorePlayer.value;
	scoreEnemy.elem.innerHTML = scoreEnemy.value;
}

/*==========================================
Loop 
==========================================*/

function loop() {
	requestAnimationFrame(loop);
	update();
	render();
}

/*==========================================
Let's Play! 
==========================================*/

init(); // to win it!

/*==========================================
Non-Gameplay Related Scaling
==========================================*/

var gameWrap = document.querySelector('body'),
	game = document.querySelector('.pong'),
	gamePadding = 0.15,
	gameBcr,
	gameWidth,
	gameHeight,
	gameRatio,
	gameScale,
	gameWrapWidth,
	gameWrapHeight;
	
function setScale() {
	game.style.transform = 'translateX(-50%) translateY(-50%) scale(1)';
	gameBcr = game.getBoundingClientRect();
	gameWidth = gameBcr.width;
	gameHeight = gameBcr.height;
	gameRatio = gameHeight / gameWidth;
	gameWrapWidth = gameWrap.offsetWidth - ( gameWrap.offsetWidth * gamePadding );
	gameWrapHeight = gameWrap.offsetHeight - ( gameWrap.offsetHeight * gamePadding );
	if (gameWrapWidth > gameWrapHeight / gameRatio) {
		gameScale = gameWrapHeight / gameRatio / gameWidth;
	} else {
		gameScale = gameWrapWidth * gameRatio / gameHeight;
	}
	game.style.transform = 'translateX(-50%) translateY(-50%) scale(' + gameScale + ')';
}

function onResize() {
	setScale();
}

addEventListener('resize', onResize);

setScale();
!
999px

Console