var x = 25;
var y = 250;
var dx = 1.5;
var dy = -4;
var ctx;
var WIDTH;
var HEIGHT;
var paddlex;
var paddleh = 10;
var paddlew = 75;
var rightDown = false;
var leftDown = false;
var canvasMinX = 0;
var canvasMaxX = 0;
var intervalId = 0;
var bricks;
var NROWS = 5;
var NCOLS = 5;
var BRICKWIDTH;
var BRICKHEIGHT = 15;
var PADDING = 1;

function init() {
  ctx = $('#canvas')[0].getContext("2d");
  WIDTH = $("#canvas").width();
  HEIGHT = $("#canvas").height();
  BRICKWIDTH = (WIDTH/NCOLS) - 1;
  paddlex = WIDTH / 2;
  canvasMinX = $("#canvas").offset().left;
  canvasMaxX = canvasMinX + WIDTH;
  intervalId = setInterval(draw, 10);
  return intervalId;
}

function circle(x,y,r) {
  ctx.beginPath();
  ctx.arc(x, y, r, 0, Math.PI*2, true);
  ctx.closePath();
  ctx.fill();
}

function rect(x,y,w,h) {
  ctx.beginPath();
  ctx.rect(x,y,w,h);
  ctx.closePath();
  ctx.fill();
}

function clear() {
  ctx.clearRect(0, 0, WIDTH, HEIGHT);
  rect(0,0,WIDTH,HEIGHT);
}

function onKeyDown(evt) {
  if (evt.keyCode == 39) rightDown = true;
  else if (evt.keyCode == 37) leftDown = true;
}

function onKeyUp(evt) {
  if (evt.keyCode == 39) rightDown = false;
  else if (evt.keyCode == 37) leftDown = false;
}

$(document).keydown(onKeyDown);
$(document).keyup(onKeyUp);

function onMouseMove(evt) {
  if (evt.pageX > canvasMinX && evt.pageX < canvasMaxX) {
    paddlex = Math.max(evt.pageX - canvasMinX - (paddlew/2), 0);
    paddlex = Math.min(WIDTH - paddlew, paddlex);
  }
}

$(document).mousemove(onMouseMove);

function initbricks() {
    bricks = new Array(NROWS);
    for (i=0; i < NROWS; i++) {
        bricks[i] = new Array(NCOLS);
        for (j=0; j < NCOLS; j++) {
            bricks[i][j] = 1;
        }
    }
}

function drawbricks() {
  for (i=0; i < NROWS; i++) {
    ctx.fillStyle = rowcolors[i];
    for (j=0; j < NCOLS; j++) {
      if (bricks[i][j] == 1) {
        rect((j * (BRICKWIDTH + PADDING)) + PADDING,
             (i * (BRICKHEIGHT + PADDING)) + PADDING,
             BRICKWIDTH, BRICKHEIGHT);
      }
    }
  }
}

var ballr = 10;
var rowcolors = ["#FF1C0A", "#FFFD0A", "#00A308", "#0008DB", "#EB0093"];
var paddlecolor = "#FFFFFF";
var ballcolor = "#FFFFFF";
var backcolor = "#000000";

function draw() {
  ctx.fillStyle = backcolor;
  clear();
  ctx.fillStyle = ballcolor;
  circle(x, y, ballr);

if (rightDown) paddlex += 5;
  else if (leftDown) paddlex -= 5;
  ctx.fillStyle = paddlecolor;
  rect(paddlex, HEIGHT-paddleh, paddlew, paddleh);

drawbricks();

//want to learn about real collision detection? go read
  // http://www.metanetsoftware.com/technique/tutorialA.html
  rowheight = BRICKHEIGHT + PADDING;
  colwidth = BRICKWIDTH + PADDING;
  row = Math.floor(y/rowheight);
  col = Math.floor(x/colwidth);
  //reverse the ball and mark the brick as broken
  if (y < NROWS * rowheight && row >= 0 && col >= 0 && bricks[row][col] == 1) {
    dy = -dy;
    bricks[row][col] = 0;
  }

if (x + dx + ballr > WIDTH || x + dx - ballr < 0)
    dx = -dx;

if (y + dy - ballr < 0)
    dy = -dy;
  else if (y + dy + ballr > HEIGHT - paddleh) {
    if (x > paddlex && x < paddlex + paddlew) {
      //move the ball differently based on where it hit the paddle
      dx = 8 * ((x-(paddlex+paddlew/2))/paddlew);
      dy = -dy;
    }
    else if (y + dy + ballr > HEIGHT)
      clearInterval(intervalId);
  }

x += dx;
  y += dy;
}

init();
initbricks();

Introduction

Code
Library
Comments

Welcome! In this tutorial, we're going to create a breakout clone that you can play in your browser, using javascript and the <canvas> element.

In order to use this tutorial, you'll need a browser that supports the <canvas> element.

Before you read any further, click on the "run code" button on the left to play the game that we'll end up creating.

On every page, you'll be able to click the "run code" button to run the code we've developed so far. Every page besides this one has an editor in it containing the javascript code that will be run in the same box as the game as soon as you click the button. You can make changes to the code, and see the results instantly by clicking the "run code" button.

In order to make our lives easier, I've included the jQuery framework in every page, which extends javascript in your browser with some useful methods.

If you have any comments or questions, feel free to leave a comment on the "comments" tab.

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