Add a drop shadow to the circles

[anthony-onefoursix]

This is a great piece of code, but I was wondering how to attach a drop shadow to the circles. I myself am actually using the arc version of this, and I've been experimenting with:

ctx.shadowColor = 'black';
ctx.shadowBlur = 20;
ctx.shadowOffsetX = 20;
ctx.shadowOffsetY = 20;

but I cant get it to attach to the bars?

Any assistance would be gratefully received.