the snow is webgl and the voronoi is an svg generated by d3. needs to be tidied a little still

despite d3 claiming their voronoi implementation is much faster than alternatives, i still find it to be unacceptably slow for 200 vertices which is what i'm using currently. and it also seems to be too slow for update on scroll even though i don't recalculate the svg, just change its colour, so i wonder which parts are actually slow

i like webgl except it's challenging to debug