I have a couple of suggestions regarding the red weed and a couple other things, the red weed does work well and it looks good but when it begins to spread around it just looks like red grass and thats it and i wish that maybe the trees would go red as well as making the ground under it red.
Also maybe make the digging machines or the handling machines expand the pit around the cylinder as they do in the book, I like that you can dig as the handling machine but i wish it was expanded on a little bit, another thing is the artillery and soldiers are pretty much cosmetic and dont do much at all,
one last suggestion is to make the heat-ray slightly more powerful and make a lot more fire than it does now as it just feels very weak. Either way I love your game I think the game is executed really well keep up the good work.