straker/README.md

## README.md

      
    Raw
  

              README.md
            
          
    Basic Snake HTML and JavaScript Game

Snake is a fun game to make as it doesn't require a lot of code (less than 100 lines with all comments removed). This is a basic implementation of the snake game, but it's missing a few things intentionally and they're left as further exploration for the reader.

Further Exploration


Score

When the snake eats an apple, the score should increase by one. Use context.fillText() to display the score to the screen


Mobile and touchscreen support

Allow the game to be scaled down to a phone size. See https://codepen.io/straker/pen/VazMaL
Support touch controls


Better apple spawning

Currently the apple spawns in any random grid in the game, even if the snake is already on that spot. Improve it so it only spawns in empty grid locations


Important note: I will answer questions about the code but will not add more features or answer questions about adding more features. This series is meant to give a basic outline of the game but nothing more.
License

(CC0 1.0 Universal) You're free to use this game and code in any project, personal or commercial. There's no need to ask permission before using these. Giving attribution is not required, but appreciated.
Other Basic Games


Pong
Breakout
Tetris
Bomberman
Frogger
Missile Command
Sokoban
Doodle Jump
Puzzle Bobble
Helicopter
Block Dude

Support

Basic HTML Games are made possible by users like you. When you become a Patron, you get access to behind the scenes development logs, the ability to vote on which games I work on next, and early access to the next Basic HTML Game.
Top Patrons


Karar Al-Remahy
UnbrandedTech
Innkeeper Games
Nezteb


## snake.html
<!DOCTYPE html>
<html>
<head>
  <title>Basic Snake HTML Game</title>
  <meta charset="UTF-8">
  <style>
  html, body {
    height: 100%;
    margin: 0;
  }

  body {
    background: black;
    display: flex;
    align-items: center;
    justify-content: center;
  }
  canvas {
    border: 1px solid white;
  }
  </style>
</head>
<body>
<canvas width="400" height="400" id="game"></canvas>
<script>
var canvas = document.getElementById('game');
var context = canvas.getContext('2d');

// the canvas width & height, snake x & y, and the apple x & y, all need to be a multiples of the grid size in order for collision detection to work
// (e.g. 16 * 25 = 400)
var grid = 16;
var count = 0;

var snake = {
  x: 160,
  y: 160,

  // snake velocity. moves one grid length every frame in either the x or y direction
  dx: grid,
  dy: 0,

  // keep track of all grids the snake body occupies
  cells: [],

  // length of the snake. grows when eating an apple
  maxCells: 4
};
var apple = {
  x: 320,
  y: 320
};

// get random whole numbers in a specific range
// @see https://stackoverflow.com/a/1527820/2124254
function getRandomInt(min, max) {
  return Math.floor(Math.random() * (max - min)) + min;
}

// game loop
function loop() {
  requestAnimationFrame(loop);

  // slow game loop to 15 fps instead of 60 (60/15 = 4)
  if (++count < 4) {
    return;
  }

  count = 0;
  context.clearRect(0,0,canvas.width,canvas.height);

  // move snake by it's velocity
  snake.x += snake.dx;
  snake.y += snake.dy;

  // wrap snake position horizontally on edge of screen
  if (snake.x < 0) {
    snake.x = canvas.width - grid;
  }
  else if (snake.x >= canvas.width) {
    snake.x = 0;
  }

  // wrap snake position vertically on edge of screen
  if (snake.y < 0) {
    snake.y = canvas.height - grid;
  }
  else if (snake.y >= canvas.height) {
    snake.y = 0;
  }

  // keep track of where snake has been. front of the array is always the head
  snake.cells.unshift({x: snake.x, y: snake.y});

  // remove cells as we move away from them
  if (snake.cells.length > snake.maxCells) {
    snake.cells.pop();
  }

  // draw apple
  context.fillStyle = 'red';
  context.fillRect(apple.x, apple.y, grid-1, grid-1);

  // draw snake one cell at a time
  context.fillStyle = 'green';
  snake.cells.forEach(function(cell, index) {

    // drawing 1 px smaller than the grid creates a grid effect in the snake body so you can see how long it is
    context.fillRect(cell.x, cell.y, grid-1, grid-1);

    // snake ate apple
    if (cell.x === apple.x && cell.y === apple.y) {
      snake.maxCells++;

      // canvas is 400x400 which is 25x25 grids
      apple.x = getRandomInt(0, 25) * grid;
      apple.y = getRandomInt(0, 25) * grid;
    }

    // check collision with all cells after this one (modified bubble sort)
    for (var i = index + 1; i < snake.cells.length; i++) {

      // snake occupies same space as a body part. reset game
      if (cell.x === snake.cells[i].x && cell.y === snake.cells[i].y) {
        snake.x = 160;
        snake.y = 160;
        snake.cells = [];
        snake.maxCells = 4;
        snake.dx = grid;
        snake.dy = 0;

        apple.x = getRandomInt(0, 25) * grid;
        apple.y = getRandomInt(0, 25) * grid;
      }
    }
  });
}

// listen to keyboard events to move the snake
document.addEventListener('keydown', function(e) {
  // prevent snake from backtracking on itself by checking that it's
  // not already moving on the same axis (pressing left while moving
  // left won't do anything, and pressing right while moving left
  // shouldn't let you collide with your own body)

  // left arrow key
  if (e.which === 37 && snake.dx === 0) {
    snake.dx = -grid;
    snake.dy = 0;
  }
  // up arrow key
  else if (e.which === 38 && snake.dy === 0) {
    snake.dy = -grid;
    snake.dx = 0;
  }
  // right arrow key
  else if (e.which === 39 && snake.dx === 0) {
    snake.dx = grid;
    snake.dy = 0;
  }
  // down arrow key
  else if (e.which === 40 && snake.dy === 0) {
    snake.dy = grid;
    snake.dx = 0;
  }
});

// start the game
requestAnimationFrame(loop);
</script>
</body>
</html>
	<!DOCTYPE html>
	<html>
	<head>
	<title>Basic Snake HTML Game</title>
	<meta charset="UTF-8">
	<style>
	html, body {
	height: 100%;
	margin: 0;
	}

	body {
	background: black;
	display: flex;
	align-items: center;
	justify-content: center;
	}
	canvas {
	border: 1px solid white;
	}
	</style>
	</head>
	<body>
	<canvas width="400" height="400" id="game"></canvas>
	<script>
	var canvas = document.getElementById('game');
	var context = canvas.getContext('2d');

	// the canvas width & height, snake x & y, and the apple x & y, all need to be a multiples of the grid size in order for collision detection to work
	// (e.g. 16 * 25 = 400)
	var grid = 16;
	var count = 0;

	var snake = {
	x: 160,
	y: 160,

	// snake velocity. moves one grid length every frame in either the x or y direction
	dx: grid,
	dy: 0,

	// keep track of all grids the snake body occupies
	cells: [],

	// length of the snake. grows when eating an apple
	maxCells: 4
	};
	var apple = {
	x: 320,
	y: 320
	};

	// get random whole numbers in a specific range
	// @see https://stackoverflow.com/a/1527820/2124254
	function getRandomInt(min, max) {
	return Math.floor(Math.random() * (max - min)) + min;
	}

	// game loop
	function loop() {
	requestAnimationFrame(loop);

	// slow game loop to 15 fps instead of 60 (60/15 = 4)
	if (++count < 4) {
	return;
	}

	count = 0;
	context.clearRect(0,0,canvas.width,canvas.height);

	// move snake by it's velocity
	snake.x += snake.dx;
	snake.y += snake.dy;

	// wrap snake position horizontally on edge of screen
	if (snake.x < 0) {
	snake.x = canvas.width - grid;
	}
	else if (snake.x >= canvas.width) {
	snake.x = 0;
	}

	// wrap snake position vertically on edge of screen
	if (snake.y < 0) {
	snake.y = canvas.height - grid;
	}
	else if (snake.y >= canvas.height) {
	snake.y = 0;
	}

	// keep track of where snake has been. front of the array is always the head
	snake.cells.unshift({x: snake.x, y: snake.y});

	// remove cells as we move away from them
	if (snake.cells.length > snake.maxCells) {
	snake.cells.pop();
	}

	// draw apple
	context.fillStyle = 'red';
	context.fillRect(apple.x, apple.y, grid-1, grid-1);

	// draw snake one cell at a time
	context.fillStyle = 'green';
	snake.cells.forEach(function(cell, index) {

	// drawing 1 px smaller than the grid creates a grid effect in the snake body so you can see how long it is
	context.fillRect(cell.x, cell.y, grid-1, grid-1);

	// snake ate apple
	if (cell.x === apple.x && cell.y === apple.y) {
	snake.maxCells++;

	// canvas is 400x400 which is 25x25 grids
	apple.x = getRandomInt(0, 25) * grid;
	apple.y = getRandomInt(0, 25) * grid;
	}

	// check collision with all cells after this one (modified bubble sort)
	for (var i = index + 1; i < snake.cells.length; i++) {

	// snake occupies same space as a body part. reset game
	if (cell.x === snake.cells[i].x && cell.y === snake.cells[i].y) {
	snake.x = 160;
	snake.y = 160;
	snake.cells = [];
	snake.maxCells = 4;
	snake.dx = grid;
	snake.dy = 0;

	apple.x = getRandomInt(0, 25) * grid;
	apple.y = getRandomInt(0, 25) * grid;
	}
	}
	});
	}

	// listen to keyboard events to move the snake
	document.addEventListener('keydown', function(e) {
	// prevent snake from backtracking on itself by checking that it's
	// not already moving on the same axis (pressing left while moving
	// left won't do anything, and pressing right while moving left
	// shouldn't let you collide with your own body)

	// left arrow key
	if (e.which === 37 && snake.dx === 0) {
	snake.dx = -grid;
	snake.dy = 0;
	}
	// up arrow key
	else if (e.which === 38 && snake.dy === 0) {
	snake.dy = -grid;
	snake.dx = 0;
	}
	// right arrow key
	else if (e.which === 39 && snake.dx === 0) {
	snake.dx = grid;
	snake.dy = 0;
	}
	// down arrow key
	else if (e.which === 40 && snake.dy === 0) {
	snake.dy = grid;
	snake.dx = 0;
	}
	});

	// start the game
	requestAnimationFrame(loop);
	</script>
	</body>
	</html>