A capacity/fill-progress meter rendered as a glassblower's parison inflating: a thick-walled bubble grows from a small dense core toward a larger, thin-walled sphere on a self-limiting exponential curve that visibly decelerates as it grows, wall thickness thinning in proportion to the radius the way real blown glass thins, then holding at the 'about to over-blow' beat before deflating and reheating to blow again.