Reference

• ​http://en.wikipedia.org/wiki/Canvas_element
• ​http://wiki.moztw.org/%E7%94%A8_Canvas_%E7%95%AB%E5%9C%96
• ​http://billmill.org/static/canvastutorial/index.html
• ​http://www.c3dl.org/index.php/tutorials/tutorial-1-browsers/