Minecraft, if you haven't heard of it well...
Basically it's a game of building blocks, almost like Legos but not exactly.
There is a day and night with a nice touch of Zombies Spiders and Creepers (oh my!)
It is not just flat plains but mountains up in the clouds, giant caverns and vast oceans.
Here is a funny music video showing you Minecraft :D
There is so much to explore and build and there is nothing stopping you... except maybe for the arrow-firing skeletons.
The hardest part of Minecraft is one thing... surviving your first night, and if you have a problem with that you should watch this series.
Oh and if you go to their website and make a user, you can play the beta single player for free! I haven't bought the full version yet but I know it's awesome.
Creepers keep on creeping -Adam