Acre
Acres are grid elements measuring 16x16 spaces and can be thought of as a basic unit of the player's town map. Each game in the Animal Crossing series arranges these preconstructed acres in novel ways to generate thousands of different possible town layouts. In all games prior to and including Template:AFe+ there was an explicitly designated acre system viewable from the map screen. Subsequent titles removed the explicit acre system in favor of an open and scrolling rounded-world design, although the acres are still used to determine perfect town status (Animal Crossing: New Leaf being the exception).
In Animal Crossing: amiibo Festival, Template:AF+, Animal Crossing and Template:AFe+
These games feature the largest town map in the Animal Crossing series measuring six acres across by five down. Town maps are generated semi-randomly; some acre models may only appear in a designated space (the Train Station is always located in Acre A-3) while others are more flexible.
In a new town, the only time two trees will be diagonally adjacent is when they are in adjacent acres. Each day, a maximum of 30 oak or cedar trees will drop 100 bells when shaken, a beehive will spawn in up to five other random trees and up to two other random trees will spawn a furniture item. Note that if a certain tree minimum is not met all the beehives and furniture items will not spawn. Tree count minimums also apply when trying to achieve a perfect town rating.
Every time the player moves into an acre (with the exception of a player exiting their house upon loading the game), one fish and one bug spawn at the locations programmed within the acre data. The bug and fish within the acre disappear upon moving six squares away from that acre. Bugs cannot move outside of an acre; should a banded dragonfly fly outside of the acre it will fly up and disappear. However, fish can move with the river current and end up in the next acre. The bug and fish that appear in the acre are determined by their rarity.
In Animal Crossing: Wild World
Wild World is the first game in the series to feature a scrolling rounded-world design. Each town is made up of only 16 acres (four across and four down), giving Wild World the smallest town map of any game in the Animal Crossing series. Explicit acre boundaries don't exist, however they are still used in the game's code to determine perfect town status. Each day a maximum of 16 oak or cedar trees will drop 100 bells when shaken, up to four trees will contain a beehive, and up to two will hold a piece of furniture.
Fish and bugs no longer spawn upon entering an acre, instead they appear in designated spawn locations out of viewing range of the camera. Up to one bug or fish may appear in a given spawn location at a time, however unlike previous games in the series, there is a not a 100% chance of a bug or fish appearing in each acre. A bug or fish's rarity also affects the likelihood of its appearance.
In Animal Crossing: City Folk
The terrain models are very similar to the terrain models in Wild World and the acres in the N64 and GCN Animal Crossing games, and function in much the same way as Wild World. As in Wild World, it uses a cylinder-like mapping structure, which means the terrain models are curved in City Folk as well. There are still 16x16 squares, as it was in previous games, but there are only 25 acres, unlike both its predecessors. City Folk has two separate cylinder-like maps, which is the town and the city.
The ratio of beehives, furniture and bells per acre is identical to Animal Crossing. Like Wild World, City Folk has continuous scrolling and does not use an acre system or display acre boundaries on the map. Just as in Wild World, by looking closely at the river, there will be a slight crack in the river banks when they cross the terrain model edge.
City Folk uses the very same percentage roulette system for bugs and fish in spawn spots as it was in Wild World, however fish now spawn in the spawn spots in viewing range of the camera as well as out of viewing range, but bugs remain the same in regards to spawning outside of viewing range.
In Animal Crossing: New Leaf
New Leaf has cliffs separating the town from the beach. Due to the improved processing power and expanded cartridge memory of the Nintendo 3DS, the map is bigger. New Leaf retains the cylinder-like mapping structure from it's previous two predecessors. It also has eight separate cylinder-like maps, which is the town, the ocean to Tortimer Island, Tortimer Island, the Main Street and the four parts of the Happy Home Showcase. Compared to City Folk where it only had two cylinder-like maps.
Villager's homes, town projects, buildings and player's own house can be built anywhere as long as it's two spaces away from the river (except if it's a bridge), the building, the cliff wall, the plaza or near the train track fence. It doesn't even have to matter if it's between two terrain models in the town. Unlike in City Folk and it's predecessors where it used signposts to indicate villager's home to be build on, New Leaf no longer uses signposts for villager's houses, as they are built anywhere around town where there is the least amount of trees.
Bug and fish spawn spots remain the same as they did in City Folk, with the same style of spawning.
