Note: If you’re not using IE, you’re probably not seeing anything wrong. But if you’re using IE, then the height of the SVG is 150px, no matter how many times you refresh the browser – that’s not cool.
With nice browsers, every time you refresh the page the SVG height adjusts to contain a line of circles that always fills the light gray box. Most modern browsers will set the SVG and container height according to the aspect ratio of the viewbox attribute, and the SVG will fill the width of the page.
But not IE (tested with IE 9, 10 & 11): IE sets the SVG height to 150px, regardless of the aspect ratio of the SVG. So the you’ll probably see a random amount of empty gray space to the right of the circles every time you refresh. Click here for a solution to the IE problem.