Landspotting (www.landspotting.org), a recently released game for the iPad, allows players to characterize the landscape into simple and general land cover types (e.g. Urban, Trees, Grass, Water, Snow and Ice, Unknown, etc.) using their fingers to paint on high resolution satellite imagery. It is a tower-defense-game whereby players earn coins to buy new buildings, more warriors, and resources. The better the player paints, the more houses added to your village and the more warriors you have to protect against invaders.
However, the underlying goal of this game is crowd-sourcing the validation of global land cover types in order to improve global satellite-based land cover maps and products. The game was developed in cooperation with the Geo-Wiki.org project (http://www.geo-wiki.org). The game can be downloaded from iTunes.