Setting graphics to low using mouseclic only affects the foreground. Having a way to lower all the graphics would be great for people with slower computers. I also imagine that the animation in the lava takes up a bit of processing power.
If this was supposed to be a seperate game with a seperate story, I'd have liked an ending. Like finding a big batch of fuel for the heli and driving back (in the green vehicle). The reason this feels like a demo is that the moment you find new, intresting stuff the game gets cut off without an ending.