todo.txt

* add temperature equalizing, and temp-based ignition
* add wind or force

* need a way of displaying a framerate or frame draw time without itself affecting performance
* make it possible to speed up or slow down (by simulating multiple generations before redrawing)
* maybe make the pixel scale adjustable



* the window size should adapt so that it's usable on mobile
* there is an issue when pouring sand into water, since the column of sand is continuous to the top, the water will actually flow up until it gets to where the
  mouse is, and then squirts out sideways, usually to the left.  There is currently no way for the water to move sideways and displace a third cell from the
  equation.  It can only swap places with a cell



* make it possible to change the simulator backend (but right now, the alternative backends aren't working)