Tried the demo and had to go further. Got to a point where I was setting up defences then I got eaten. Started again this morning, had 2 games and both only lasted 25-30 minutes before I got attacked and eaten. Tricky little game, quite addictive though.
Make a gun pretty early on and try to not put your base near the wolves (or whatever they are). And you should be fine. After that you will need turrets.