From Wikipedia: The objective of Animal Crossing: Wild World is to pay off a debt to Tom Nook, who allows the player to move into a house he owns. If the mortgage is paid off, the player's house will expand until an upstairs, left, right, center and back room are included. After the first loan is paid, for 19,800 bells, the loan expands. This is slightly different from the first game, in which the finished house only consisted of a basement, a main room, and an attic. While paying off a debt, the player can perform a variety of optional tasks, including interacting with other villagers and filling the catalog of items attainable in the game, such as furniture, Groyoids, clothes and stationery. Animal Crossing: Wild World is entirely non-linear and does not require the player to pay off their mortgage immediately. Unlike the previous game, all the players characters share the same house and work to pay off the same mortgage, instead of each having their own house.
Animal Crossing: Wild World makes use of several of the Nintendo DS's features, including the touch screen, dual screens, and internal clock. The touch screen is used for menu navigation and interacting with the surrounding area, including movement, using tools, talking to other villagers, entering buildings, picking up items, etc. The dual screens are used to display the overworld on the touch screen and the sky on the top screen, by time of day and season. The internal clock is used to great extent; like the previous game in the series, Animal Crossing: Wild World uses the internal clock so that the game can be played in real-time (or according to what time it is on the player's DS). The environment changes based on the time of day and the season; for instance, as it gets later in the evening, the sky goes from orange to dark blue, and the weather changes depending on what season it is on the calendar. The game also has events which take place on certain days, including "Yay Day", "La-Di-Day", Fishing, Bug, and Flower tourneys, Acorn Festival and the Flea Market. Unlike the first Animal Crossing game, it does not include any real-world holidays, such as Valentine's Day, April Fools' Day, Halloween, Christmas, etc. However, it does have a New Year's countdown from December 31st until the new year.
