(The main, survival mode)
This is game is awesome. I can't explain it to you myself, if you want to know the gist of it, watch this:http://www.youtube.com/watch?v=ylVtj-1Ccgg
This game is extremely fun. Though, it's not everyone's style of game so if you don't like the looks of it, I understand. But, you should still take advantage of this weekend at least to try it. It seems like this is only a free-to-play weekend, so you'll have to pay for it to keep playing after the weekend's up. When I first started this game, I had my doubts, but I can now say I'm thoroughly addicted.
Go try it!