function set_canvas(width, height) {
	var canvas = document.createElement('canvas') ;
	canvas.setAttribute('width', width) ;
	canvas.setAttribute('height', height) ;
	return canvas ;
}

function set_stage(width, height) {
	var stage = document.createElement('div') ;
	stage.style.width           = width ;
	stage.style.height          = height ;
	stage.style.position        = 'relative' ;
	stage.style.margin          = 0 ;
	stage.style.transformOrigin = "0 0"; // scale from top left
	return stage ;
}

function draw_circle(ctx, circ) {
  ctx.beginPath() ;
  var x = circ.x ;
  var y = circ.y ;
  var r = circ.radius ;
  ctx.arc(x, y, r, 0, Math.PI * 2, true) ;
  ctx.fillStyle = circ.color ;
  ctx.fill() ;
  ctx.closePath() ;
}

var gameDiv = document.getElementById('#game_div') ; // assume there is some element called game_div
var bgclr = '#FFF' ;

document.body.style.backgroundColor = bgclr ;
document.body.style.overflowY = 'hidden';
document.body.style.margin = 0 ;

gameDiv.style.margin = 0 ;
gameDiv.style.height = '100%' ;
gameDiv.style.width = '100%' ;
gameDiv.style.font = '13pt courier';
gameDiv.style.fontWeight = 'bold';
gameDiv.style.backgroundColor = bgclr ;
gameDiv.style.overflowY = 'hidden';
gameDiv.style.color = '#ccc';
gameDiv.style['-webkit-user-select'] = 'none';
gameDiv.style['-moz-user-select'] = 'none';
gameDiv.style['user-select'] = 'none' ;        

var size   = 100 ;
var width  = size ;
var height = size ;
var dur    = 500 ; // transition duration in milliseconds
var perf   = window.performance ;

var canvas = set_canvas(width, height) ;
canvas.setAttribute('id', 'vizCanvas') ;
canvas.style.position = 'absolute' ;

var hiddenCanvas = set_canvas(width, height) ;
hiddenCanvas.style.display = 'none' ; // hide this canvas

var context                         = canvas.getContext('2d') ;  
// context.webkitImageSmoothingEnabled = false ; 
context.mozImageSmoothingEnabled    = false ;
context.imageSmoothingEnabled       = false ;
context.font                        = "48px Arial" ; 
context.globalAlpha                 = 1.0 ;

var stage = set_stage(width, height) ;
stage.appendChild(canvas) ;
gameDiv.appendChild(stage) ;

var circ = {x: width * 0.5, y: height * 0.5, radius: width * 0.5, color: '#39A'} ;
draw_circle(context, circ) ;