rect(100,100,50,60).delay(2).to({fillStyle:'#999'},1)
rect(60,60,150,100).to({x:50,width:100,y:100,fillStyle:"#fff"},1)
rect(40,60,50,100).delay(2).to({rotate:90, x:160,y:50, fillStyle:"#999"},1)
text('(a+b)(a-b)=a^2-b^2', 60, 170)
text("a",100,37)
text("b",180,37)
text({text:'a-b',color:'rgba(0,0,0,0)'},220,70).delay(2).to({fillStyle:"#555"},1)