Canvas Tutorial - Introduction

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;
var ballr = 10;

var rowcolors = ["#FF1C0A", "#FFFD0A", "#00A308", "#0008DB", "#EB0093"];
var paddlecolor = "#FFFFFF";
var ballcolor = "#FFFFFF";
var backcolor = "#222222";

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 ontouchMover(e) {
 if(e.touches.length == 1){ // Only deal with one finger
    var touch = e.touches[0]; // Get the information for finger #1
    paddlex = Math.max(touch.pageX - canvasMinX - (paddlew/2), 0);
    paddlex = Math.min(WIDTH - paddlew, paddlex);
  }
}

$(document).ontouchmove(ontouchMover);

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.harveycartel.org/metanet/tutorials/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;
}

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;
}

init();
initbricks();
draw();