Oh...and you don't *HAVE* to clear the canvas and start over for *ANY* change.
Say you wanted to change one cell from grass to concrete: You could do that by just re-writing that part of the canvas.
Or, if you didn't use a canvas, by just changing the src property of one of your <img> tags.
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.