grabcode/index.html

## index.html
<!DOCTYPE html>
<head>
  <meta charset="UTF-8">
  <title>Text-based snake game</title>
  <style>
    #board {
      border: 3px solid;
      float: left;
      font-size: 24px;
      line-height: 1.5ex;
      margin: 10px;
    }
  </style>
</head>
<body>
  <pre id="board"></pre>
  <p id="score"></p>
  <button id="restart" style="display:none;">Restart</button>
  <script src="widget.js"></script>
</body>

## widget.js
// Subtasks;
// done: snake navigating edge to edge
// done: generate randomly located fruit
// todo: exclude any occupied snake location from fruit's candidate locations
// done: increasing snake's size when eating a fruit
// done: snake's tail following its head
// done: game over when snake eat itself
// done: preventing snake suddenly going opposite of current direction
// todo: diamonds
// todo (stretch): second snake

let startGameLoop = true;

const boardWidth = 16;
const boardHeight = 10;
const board = document.getElementById('board');
const score = document.getElementById('score');
const restart = document.getElementById('restart');

const keyToDirection = {
  'ArrowUp': { x: 0, y: -1, opposite: 'ArrowDown' },
  'ArrowRight': { x: 1, y: 0, opposite: 'ArrowLeft' },
  'ArrowDown': { x: 0, y: 1, opposite: 'ArrowUp' },
  'ArrowLeft': { x: -1, y: 0, opposite: 'ArrowRight' },
};

function initSnake() {
  return {
    x: boardWidth / 2,
    y: boardHeight / 2,
    tail: [
      { x: boardWidth / 2 - 1, y: boardHeight / 2},
      { x: boardWidth / 2 - 2, y: boardHeight / 2},
    ],
    direction: keyToDirection['ArrowRight'],
  };
}

const snake = {
  ...initSnake(),
};

function gameOver() {
  computeAndDisplayScore();
  restart.style.display = 'block';
  startGameLoop = !startGameLoop;
}

function gameOn() {
  score.innerHTML = ''
  restart.style.display = 'none';
  startGameLoop = !startGameLoop;
  Object.assign(snake, initSnake());
}

function getRandomInt(max) {
  return Math.floor(Math.random() * max);
}

function generateRandomFruitPosition() {
  const x = getRandomInt(boardWidth);
  const y = getRandomInt(boardHeight);
  return {x , y};
}

const fruit = generateRandomFruitPosition();

function renderBoard() {
  let newBoard = '';
  for (let y = 0; y < boardHeight; y++) {
    for (let x = 0; x < boardWidth; x++) {
      let char = ' ';
      if (x === snake.x && y === snake.y) {
        char = '*';
      } else if (x === fruit.x && y === fruit.y) {
        char = '+';
      }

      snake.tail.forEach(pieceOfTail => {
        if (pieceOfTail.x === x && pieceOfTail.y === y) {
          char = '*';
        }
      });

      newBoard += char;
    }
    newBoard += '\n';
  }
  board.textContent = newBoard;
}

function computeAndDisplayScore() {
  score.innerHTML = `Score: ${snake.tail.length * 10}`;
}

function gameLoop() {
  snake.tail.splice(0, 0, {
    x: snake.x,
    y: snake.y
  });

  snake.x += snake.direction.x;
  snake.y += snake.direction.y;
  snake.x = (boardWidth + snake.x) % boardWidth;
  snake.y = (boardHeight + snake.y) % boardHeight;

  snake.tail.forEach((pieceOfTail) => {
    if (pieceOfTail.x === snake.x && pieceOfTail.y === snake.y) {
      gameOver();
    }
  });

  if (fruit.x === snake.x && fruit.y === snake.y) {
    const newFruit = generateRandomFruitPosition();
    fruit.x = newFruit.x;
    fruit.y = newFruit.y;
  } else {
    snake.tail.pop();
  }

  renderBoard();
}

renderBoard();
setInterval(() => {
  startGameLoop && gameLoop();
}, 200);

document.addEventListener('keydown', e => {
  if (keyToDirection[e.key] && e.key !== snake.direction.opposite) {
    snake.direction = keyToDirection[e.key];
  }
});

restart.addEventListener('click', () => gameOn());
	<!DOCTYPE html>
	<head>
	<meta charset="UTF-8">
	<title>Text-based snake game</title>
	<style>
	#board {
	border: 3px solid;
	float: left;
	font-size: 24px;
	line-height: 1.5ex;
	margin: 10px;
	}
	</style>
	</head>
	<body>
	<pre id="board"></pre>
	<p id="score"></p>
	<button id="restart" style="display:none;">Restart</button>
	<script src="widget.js"></script>
	</body>
	// Subtasks;
	// done: snake navigating edge to edge
	// done: generate randomly located fruit
	// todo: exclude any occupied snake location from fruit's candidate locations
	// done: increasing snake's size when eating a fruit
	// done: snake's tail following its head
	// done: game over when snake eat itself
	// done: preventing snake suddenly going opposite of current direction
	// todo: diamonds
	// todo (stretch): second snake

	let startGameLoop = true;

	const boardWidth = 16;
	const boardHeight = 10;
	const board = document.getElementById('board');
	const score = document.getElementById('score');
	const restart = document.getElementById('restart');

	const keyToDirection = {
	'ArrowUp': { x: 0, y: -1, opposite: 'ArrowDown' },
	'ArrowRight': { x: 1, y: 0, opposite: 'ArrowLeft' },
	'ArrowDown': { x: 0, y: 1, opposite: 'ArrowUp' },
	'ArrowLeft': { x: -1, y: 0, opposite: 'ArrowRight' },
	};

	function initSnake() {
	return {
	x: boardWidth / 2,
	y: boardHeight / 2,
	tail: [
	{ x: boardWidth / 2 - 1, y: boardHeight / 2},
	{ x: boardWidth / 2 - 2, y: boardHeight / 2},
	],
	direction: keyToDirection['ArrowRight'],
	};
	}

	const snake = {
	...initSnake(),
	};

	function gameOver() {
	computeAndDisplayScore();
	restart.style.display = 'block';
	startGameLoop = !startGameLoop;
	}

	function gameOn() {
	score.innerHTML = ''
	restart.style.display = 'none';
	startGameLoop = !startGameLoop;
	Object.assign(snake, initSnake());
	}

	function getRandomInt(max) {
	return Math.floor(Math.random() * max);
	}

	function generateRandomFruitPosition() {
	const x = getRandomInt(boardWidth);
	const y = getRandomInt(boardHeight);
	return {x , y};
	}

	const fruit = generateRandomFruitPosition();

	function renderBoard() {
	let newBoard = '';
	for (let y = 0; y < boardHeight; y++) {
	for (let x = 0; x < boardWidth; x++) {
	let char = ' ';
	if (x === snake.x && y === snake.y) {
	char = '*';
	} else if (x === fruit.x && y === fruit.y) {
	char = '+';
	}

	snake.tail.forEach(pieceOfTail => {
	if (pieceOfTail.x === x && pieceOfTail.y === y) {
	char = '*';
	}
	});

	newBoard += char;
	}
	newBoard += '\n';
	}
	board.textContent = newBoard;
	}

	function computeAndDisplayScore() {
	score.innerHTML = `Score: ${snake.tail.length * 10}`;
	}

	function gameLoop() {
	snake.tail.splice(0, 0, {
	x: snake.x,
	y: snake.y
	});

	snake.x += snake.direction.x;
	snake.y += snake.direction.y;
	snake.x = (boardWidth + snake.x) % boardWidth;
	snake.y = (boardHeight + snake.y) % boardHeight;

	snake.tail.forEach((pieceOfTail) => {
	if (pieceOfTail.x === snake.x && pieceOfTail.y === snake.y) {
	gameOver();
	}
	});

	if (fruit.x === snake.x && fruit.y === snake.y) {
	const newFruit = generateRandomFruitPosition();
	fruit.x = newFruit.x;
	fruit.y = newFruit.y;
	} else {
	snake.tail.pop();
	}

	renderBoard();
	}

	renderBoard();
	setInterval(() => {
	startGameLoop && gameLoop();
	}, 200);

	document.addEventListener('keydown', e => {
	if (keyToDirection[e.key] && e.key !== snake.direction.opposite) {
	snake.direction = keyToDirection[e.key];
	}
	});

	restart.addEventListener('click', () => gameOn());