[x] only spawn new ones from the outer edge, so they're always visible
[ ] limit the number total allowed
[x] pause setInterval() onblur? Or how does D3 do it, since if it's in view in a window behind the working window, it's still running, but if you switch tabs it pauses
[ ] some sort of splashing-circle animation when click, instead of just spawning a line without explanation (material design ripple?)
[x] show in footer
[ ] fix mobile
[x] remove tagline, thin content padding
[ ] randomly triggers resize events on scroll, forcing redraw
[x] click should not still spawn when scrolled away from header or footer - to do this, main should not propagate the event up to body