HTML5 Snake Game

Snake game and javascript source code

This is my modification of the HTML5 snake game seen in thecodeplayer.com. You can change all the start parameters using the input form below, just remember to hit r to reload so that the new values take effect. It is very customizable, try it!

p - pause game    r - restart game

Options

Square
Circle
Width (in blocks):
Height (in blocks):
Size of blocks (px):
Background colour:
Snake colour:
Food colour:
Velocity (higher is slower):

Below is the javascript code, if you need it. You can also get it here. Of course you’ll need jQuery and some form input fields to get the initial values from in your html page, but this is not difficult to work out at all.

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$(document).ready(
		function() {
			// GLOBAL VARIABLES
			// Canvas stuff
			canvas = $("#snakecanvas")[0];
			ctx = canvas.getContext("2d");


			// LOCAL VARIABLES
			var d, pause = false;
			var food;
			var score;
			var shape;
			// Snake array
			var snake_array;

			// Initialization function
			function init(interval) {
				d = "right";
				updateCanvasSize();
				// block size
				cw = parseInt($('#snakeoptions input:text[name="size"]').val());
				// block shape
				shape = $('#snakeoptions input:radio[name="shape"]:checked').val();
				bgcol = $('#snakeoptions input:text[name="bgcol"]').val();
				snakecol = $('#snakeoptions input:text[name="snakecol"]').val();
				foodcol = $('#snakeoptions input:text[name="foodcol"]').val();

				create_snake();
				create_food();
				score = 0;
				if (typeof game_loop != "undefined")
					clearInterval(game_loop);
				game_loop = setInterval(paint, interval);
			}
			init(parseInt($('#snakeoptions input:text[name="velocity"]').val()));

			function create_snake() {
				var length = 4; // Initial length of the snake
				snake_array = [];
				for ( var i = length - 1; i >= 0; i--) {
					// Create snake starting from top left
					snake_array.push({
						x : i,
						y : 0
					});
				}
			}

			function create_food() {
				food = {
					x : Math.round(Math.random() * (w - cw) / cw),
					y : Math.round(Math.random() * (h - cw) / cw),
				};
			}

			// Paint the snake
			function paint() {
				if (pause){
					writeText("Game paused", "white", 5, h-5, "15pt")
					return;
				}

				ctx.fillStyle = bgcol;
				ctx.fillRect(0, 0, w, h);
				ctx.strokeStyle = "black";
				ctx.strokeRect(0, 0, w, h);

				var nx = snake_array[0].x;
				var ny = snake_array[0].y;

				if (d == "right")
					nx++;
				else if (d == "left")
					nx--;
				else if (d == "up")
					ny--;
				else if (d == "down")
					ny++;

				// Lets add the game over clauses now
				if (nx == -1 || nx == w / cw || ny == -1 || ny == h / cw
						|| check_collision(nx, ny, snake_array)) {
					// restart game
					init(parseInt($('#snakeoptions input:text[name="velocity"]').val()));
					return;
				}

				// Lets write the code to make the snake eat the food
				if (nx == food.x && ny == food.y) {
					var tail = {
						x : nx,
						y : ny
					};
					score+=10;
					create_food();
				} else {
					var tail = snake_array.pop();
					tail.x = nx;
					tail.y = ny;
				}

				snake_array.unshift(tail);

				for ( var i = 0; i < snake_array.length; i++) {
					var c = snake_array[i];
					// Lets paint 10px wide cells
					paint_cell(c.x, c.y, snakecol);
				}

				// Lets paint the food
				paint_cell(food.x, food.y, foodcol);
				// Lets paint the score
				var score_text = "Score: " + score;
				writeText(score_text, "black", w-80, h-5, "10pt");

			}

			function writeText(text, color, px, py, fontSize){
				ctx.fillStyle = color;
				ctx.font = fontSize + " Calibri";
				ctx.fillText(text, px, py);
			}

			// Lets first create a generic function to paint cells
			function paint_cell(x, y, color, shp) {
				strokeStyle = "black"
				if (shape == "square") {
					ctx.fillStyle = color;
					ctx.fillRect(x * cw, y * cw, cw, cw);
					ctx.strokeStyle = strokeStyle;
					ctx.strokeRect(x * cw, y * cw, cw, cw);
				} else if (shape == "circle") {
					ctx.beginPath();
					ctx.arc(x * cw + cw / 2, y * cw + cw / 2, cw / 2, 0,
							2 * Math.PI, false);
					ctx.fillStyle = color;
					ctx.strokeStyle = strokeStyle;
					ctx.fill();
					ctx.stroke();
				}
			}

			function check_collision(x, y, array) {
				for ( var i = 0; i < array.length; i++) {
					if (array[i].x == x && array[i].y == y)
						return true;
				}
				return false;
			}

			// Lets add the keyboard controls now
			$(document).keydown(function(e) {
				var key = e.which;
				// We will add another clause to prevent reverse gear
				if (key == "37" && d != "right")
					d = "left";
				else if (key == "38" && d != "down")
					d = "up";
				else if (key == "39" && d != "left")
					d = "right";
				else if (key == "40" && d != "up")
					d = "down";

				// Key -> p - toggle pause
				if (key == "80")
					pause = !pause;

				// Key -> r - restart
				if(key == "82")
					init(parseInt($('#snakeoptions input:text[name="velocity"]').val()));
			})
});
function updateCanvasSize(){
	w = parseInt($('#snakeoptions input:text[name="canvaswidth"]').val()) 
       * parseInt($('#snakeoptions input:text[name="size"]').val());
	h = parseInt($('#snakeoptions input:text[name="canvasheight"]').val()) 
       * parseInt($('#snakeoptions input:text[name="size"]').val());
	canvas.width = w;
	canvas.height = h;
}
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