Playing in your own world where you create land, mountains, trees and other stuff is always an interesting piece with creativity. One strong player from Ludum Dare competition is here.
You begin on a grid place with basic material. The trick is that you have to put the cubes so the combine into more sophisticated things. For example two basic soils make grass, two grass pieces make tress, two trees make more trees, until you get on big tree. There, you get more items and something like power, so use them wisely to create your own world. It’s very creative, addictive and hard.