Mary-Kate and Ashley Olsen have decided they want their 'sweet 16' birthday to be the best! They gather their two close friends and instruct them to go around town and pick up as many friends as possible, and the one who does is the winner of their little game. The game plays out on two levels. In the first, players advance from space to space along a board game track. Each space has a mini-game which requires the players to ride ATVs, jet skis, cars, go rock climbing, or perform other adventure related tasks. Successfully completing the games will allow a player to pick up friends and eventually win the game.
There are four players your can choose from, each with respected colors, including Mary-Kate, Ashley, Claire and Tiffany (blue, red, yellow and green, respectfully.) At the beginning of the game, each player picks which character they want to be, and a number wheel of one to ten is spun for each. The player stops the wheel whenever they choose, and highest number gets to play first, second highest plays next etc. You are in a car that is your avatar's respected color and for the first round, you move as many spaces as your number wheel stopped on. (For each level, you spin the number wheel again.) The kind of marker you land on in the road could signify many different events. The winner of each events gets a certain number of coins which can be used to buy things like gas, if needed.
Single Player Challenge- only the player in the car gets to play a game, randomly chosen (though in some cases, what you see around the car gives hints to what game you're getting. For example, if your car parks next to the ocean with canoes in the water, you have a higher chance of getting a rafting game.)
Multi-player Challenge- Same as the single player, but this time you could play with one, two, or all the other players. The teams are divided at random, but for certain games (like tag) it might be 3 against one, so the player who landed on the marker is the 1 against the other 3.
'Bad' Events- Any number of 'bad' events can occur to the player. You can get sent back on the board however many spaces you roll on the number wheel, there can be an earthquake, roadblock, your car breaks down, or you loose a friend out of your car.
Pick Up a Friend- The closest friend on the sidewalk will get into your car with you. Adding friends can normally make any player first place if you have more. The player can add up to three friends in their car, but these friends do not help with challenges and can leave the car if a 'bad' event occurs.
At the end of the game, the player who has the most coins and picked up the most friends is the winner, regardless of who actually makes it to the finish line first.
Source: Wikipedia, "Mary-Kate and Ashley: Sweet 16", available under the CC-BY-SA License.