1   var ctx = document.getElementById('tutorial').getContext('2d');

     2   ctx.fillRect(0,0,300,300);

     3   for (var i=0;i<3;i++) {

     4     for (var j=0;j<3;j++) {

     5       ctx.save();

     6       ctx.strokeStyle = "#9CFF00";

     7       ctx.translate(50+j*100,50+i*100);

     8       drawSpirograph(ctx,20*(j+2)/(j+1),-8*(i+3)/(i+1),10);

     9       ctx.restore();

    10     }

    11   }

    12 

    13 function drawSpirograph(ctx,R,r,O){

    14   var x1 = R-O;

    15   var y1 = 0;

    16   var i  = 1;

    17   ctx.beginPath();

    18   ctx.moveTo(x1,y1);

    19   do {

    20     if (i>20000) break;

    21     var x2 = (R+r)*Math.cos(i*Math.PI/72) - (r+O)*Math.cos(((R+r)/r)*(i*Math.PI/72))

    22     var y2 = (R+r)*Math.sin(i*Math.PI/72) - (r+O)*Math.sin(((R+r)/r)*(i*Math.PI/72))

    23     ctx.lineTo(x2,y2);

    24     x1 = x2;

    25     y1 = y2;

    26     i++;

    27   } while (x2 != R-O && y2 != 0 );

    28   ctx.stroke();

    29 }