are accumulated mainly by interacting with businesses, but also from farms and student jobs. Materials are used to build and upgrade many structures. They are accumulated by interacting with factories or sending trains from the station. Fame develops as the player interacts with neighboring territories. Fame can be used for a variety of special purchases. Experience (XP) appears as turquoise stars and builds a player's level. When experience reaches 100%, there is a reward of simoleons, one diamond, and full energy replenishment. Collectibles are items that are released by interacting with structures. These are used in developing structures after they have been bought or completing quests. Many collectibles are connected specifically with the type of building they can be released from, such as ticket stubs from attractions or x-ray plates from hospitals. Population increases unlock specific quests or buildings. It also increases the level of the mayor's house. Neighbors (other players which are befriended through Facebook) can also staff your structures when necessary, for instance facilities and farms both need a specific complement of avatars from SimCity Social friends to be fully operational. Interaction with neighbors' buildings also provide specific "friend/foe" collectibles and a more developed relationship (either positively or negatively) increases the likelihood of their appearance. City building Building can only take place on flat, solid land where trees have been bulldozed. All player constructions can be moved at no cost during game play providing the structure has reached a minimum level of development. Some existing game structures may be developed by the player, Some of these require expending purple diamonds to move. The initial city is on a small central area of developable land and a player must purchase more land for expansion using simoleons and collectible land permits. Structures fall into ten categories, some of which require a minimum city population to unlock: Roads - connect buildings together. They have no cost to build and no cost to remove. Many developments that are unconnected by roads will not function appropriately. Homes - cost one energy unit and 100 simoleons to build. They generate population as they develop, and their development depends on distance to the waterfront as well as other buildings in the locality. There is no direct way for a player to directly affect the population of a building - only indirectly by the placement of homes or population-increasing structures. The maximum population for a 2