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HTML 

              
                <body>
	<div class="container">
		<div class="info">
			<h1>2048 🚀</h1>
			<div class="score-container">
				<div class="score-title">Score</div>
				<span id="score">0</span>
			</div>
		</div>

		<span id="result">
			Join the numbers and get to the <b>2048</b> tile!</span>
		<div class="grid"></div>
	</div>
</body>

</html>
!

CSS 

              
                body {
	display: flex;
	background: whitesmoke;
	justify-content: center;
	font-family: "Open Sans", "Lato", sans-serif;
}

h1 {
	margin: 0px;
	color: black;
	font-size: 80px;
	line-height: 0.7;
}

.container {
	width: 468px;
	margin-top: 30px;
}

.info {
	display: flex;
	margin-bottom: 20px;
	justify-content: space-between;
}

.grid {
	width: 456px;
	height: 456px;
	display: flex;
	flex-wrap: wrap;
	margin-top: 20px;
	border-radius: 6px;
	background-color: beige;
	border: 7px solid black;
}

.grid div {
	margin: 7px;
	width: 100px;
	height: 100px;
	color: black;
	font-size: 60px;
	line-height: 1.6;
	font-weight: bold;
	border-radius: 3px;
	text-align: center;
	background: whitesmoke;
}

.score-container {
	width: 70px;
	height: 60px;
	color: white;
	text-align: center;
	border-radius: 3px;
	background: black;
}

#score {
	font-size: 30px;
}

.score-title {
	font-size: 16px;
}
!

JS 

              
                document.addEventListener("DOMContentLoaded", () => {
	const gridDisplay = document.querySelector(".grid");
	const scoreDisplay = document.getElementById("score");
	const resultDisplay = document.getElementById("result");
	let squares = [];
	const width = 4;
	let score = 0;

	//create the playing board
	function createBoard() {
		for (let i = 0; i < width * width; i++) {
			square = document.createElement("div");
			square.innerHTML = 0;
			gridDisplay.appendChild(square);
			squares.push(square);
		}
		generate();
		generate();
	}
	createBoard();

	//generate a new number
	function generate() {
		randomNumber = Math.floor(Math.random() * squares.length);
		if (squares[randomNumber].innerHTML == 0) {
			squares[randomNumber].innerHTML = 2;
			checkForGameOver();
		} else generate();
	}

	function moveRight() {
		for (let i = 0; i < 16; i++) {
			if (i % 4 === 0) {
				let totalOne = squares[i].innerHTML;
				let totalTwo = squares[i + 1].innerHTML;
				let totalThree = squares[i + 2].innerHTML;
				let totalFour = squares[i + 3].innerHTML;
				let row = [
					parseInt(totalOne),
					parseInt(totalTwo),
					parseInt(totalThree),
					parseInt(totalFour)
				];

				let filteredRow = row.filter((num) => num);
				let missing = 4 - filteredRow.length;
				let zeros = Array(missing).fill(0);
				let newRow = zeros.concat(filteredRow);

				squares[i].innerHTML = newRow[0];
				squares[i + 1].innerHTML = newRow[1];
				squares[i + 2].innerHTML = newRow[2];
				squares[i + 3].innerHTML = newRow[3];
			}
		}
	}

	function moveLeft() {
		for (let i = 0; i < 16; i++) {
			if (i % 4 === 0) {
				let totalOne = squares[i].innerHTML;
				let totalTwo = squares[i + 1].innerHTML;
				let totalThree = squares[i + 2].innerHTML;
				let totalFour = squares[i + 3].innerHTML;
				let row = [
					parseInt(totalOne),
					parseInt(totalTwo),
					parseInt(totalThree),
					parseInt(totalFour)
				];

				let filteredRow = row.filter((num) => num);
				let missing = 4 - filteredRow.length;
				let zeros = Array(missing).fill(0);
				let newRow = filteredRow.concat(zeros);

				squares[i].innerHTML = newRow[0];
				squares[i + 1].innerHTML = newRow[1];
				squares[i + 2].innerHTML = newRow[2];
				squares[i + 3].innerHTML = newRow[3];
			}
		}
	}

	function moveUp() {
		for (let i = 0; i < 4; i++) {
			let totalOne = squares[i].innerHTML;
			let totalTwo = squares[i + width].innerHTML;
			let totalThree = squares[i + width * 2].innerHTML;
			let totalFour = squares[i + width * 3].innerHTML;
			let column = [
				parseInt(totalOne),
				parseInt(totalTwo),
				parseInt(totalThree),
				parseInt(totalFour)
			];

			let filteredColumn = column.filter((num) => num);
			let missing = 4 - filteredColumn.length;
			let zeros = Array(missing).fill(0);
			let newColumn = filteredColumn.concat(zeros);

			squares[i].innerHTML = newColumn[0];
			squares[i + width].innerHTML = newColumn[1];
			squares[i + width * 2].innerHTML = newColumn[2];
			squares[i + width * 3].innerHTML = newColumn[3];
		}
	}

	function moveDown() {
		for (let i = 0; i < 4; i++) {
			let totalOne = squares[i].innerHTML;
			let totalTwo = squares[i + width].innerHTML;
			let totalThree = squares[i + width * 2].innerHTML;
			let totalFour = squares[i + width * 3].innerHTML;
			let column = [
				parseInt(totalOne),
				parseInt(totalTwo),
				parseInt(totalThree),
				parseInt(totalFour)
			];

			let filteredColumn = column.filter((num) => num);
			let missing = 4 - filteredColumn.length;
			let zeros = Array(missing).fill(0);
			let newColumn = zeros.concat(filteredColumn);

			squares[i].innerHTML = newColumn[0];
			squares[i + width].innerHTML = newColumn[1];
			squares[i + width * 2].innerHTML = newColumn[2];
			squares[i + width * 3].innerHTML = newColumn[3];
		}
	}

	function combineRow() {
		for (let i = 0; i < 15; i++) {
			if (squares[i].innerHTML === squares[i + 1].innerHTML) {
				let combinedTotal =
					parseInt(squares[i].innerHTML) + parseInt(squares[i + 1].innerHTML);
				squares[i].innerHTML = combinedTotal;
				squares[i + 1].innerHTML = 0;
				score += combinedTotal;
				scoreDisplay.innerHTML = score;
			}
		}
		checkForWin();
	}

	function combineColumn() {
		for (let i = 0; i < 12; i++) {
			if (squares[i].innerHTML === squares[i + width].innerHTML) {
				let combinedTotal =
					parseInt(squares[i].innerHTML) + parseInt(squares[i + width].innerHTML);
				squares[i].innerHTML = combinedTotal;
				squares[i + width].innerHTML = 0;
				score += combinedTotal;
				scoreDisplay.innerHTML = score;
			}
		}
		checkForWin();
	}

	//assign functions to keyCodes
	function control(e) {
		if (e.keyCode === 37) {
			keyLeft();
		} else if (e.keyCode === 38) {
			keyUp();
		} else if (e.keyCode === 39) {
			keyRight();
		} else if (e.keyCode === 40) {
			keyDown();
		}
	}
	document.addEventListener("keyup", control);

	function keyRight() {
		moveRight();
		combineRow();
		moveRight();
		generate();
	}

	function keyLeft() {
		moveLeft();
		combineRow();
		moveLeft();
		generate();
	}

	function keyUp() {
		moveUp();
		combineColumn();
		moveUp();
		generate();
	}

	function keyDown() {
		moveDown();
		combineColumn();
		moveDown();
		generate();
	}

	//check for the number 2048 in the squares to win
	function checkForWin() {
		for (let i = 0; i < squares.length; i++) {
			if (squares[i].innerHTML == 2048) {
				resultDisplay.innerHTML = "You WIN";
				document.removeEventListener("keyup", control);
				setTimeout(() => clear(), 3000);
			}
		}
	}

	//check if there are no zeros on the board to lose
	function checkForGameOver() {
		let zeros = 0;
		for (let i = 0; i < squares.length; i++) {
			if (squares[i].innerHTML == 0) {
				zeros++;
			}
		}
		if (zeros === 0) {
			resultDisplay.innerHTML = "You LOSE";
			document.removeEventListener("keyup", control);
			setTimeout(() => clear(), 3000);
		}
	}

	//clear timer
	function clear() {
		clearInterval(myTimer);
	}

	//add colours
	function addColours() {
		for (let i = 0; i < squares.length; i++) {
			if (squares[i].innerHTML == 0) squares[i].style.backgroundColor = "#afa192";
			else if (squares[i].innerHTML == 2)
				squares[i].style.backgroundColor = "#eee4da";
			else if (squares[i].innerHTML == 4)
				squares[i].style.backgroundColor = "#ede0c8";
			else if (squares[i].innerHTML == 8)
				squares[i].style.backgroundColor = "#f2b179";
			else if (squares[i].innerHTML == 16)
				squares[i].style.backgroundColor = "#ffcea4";
			else if (squares[i].innerHTML == 32)
				squares[i].style.backgroundColor = "#e8c064";
			else if (squares[i].innerHTML == 64)
				squares[i].style.backgroundColor = "#ffab6e";
			else if (squares[i].innerHTML == 128)
				squares[i].style.backgroundColor = "#fd9982";
			else if (squares[i].innerHTML == 256)
				squares[i].style.backgroundColor = "#ead79c";
			else if (squares[i].innerHTML == 512)
				squares[i].style.backgroundColor = "#76daff";
			else if (squares[i].innerHTML == 1024)
				squares[i].style.backgroundColor = "#beeaa5";
			else if (squares[i].innerHTML == 2048)
				squares[i].style.backgroundColor = "#d7d4f0";
		}
	}
	addColours();

	var myTimer = setInterval(addColours, 50);
});
!
999px

Console