From the Super Mario Wiki
Superstar Shootout was an online Flash game that was part of the official Mario Hoops 3-on-3 website. The game is not currently playable from any official source, as the site is defunct. Superstar Shootout was not listed in the Nintendo Arcade, the section on nintendo.com dedicated to promotional web games. Dribble Skillz, on the other hand, was.
In this game, the player has to shoot ten basketballs into a hoop. The player can aim using the left and right arrow keys, and hold the space bar to set the throwing force. When thrown, the ball will bounce off surrounding elements. The player will be awarded 50,000 points for every ball that goes into the hoop.
If the ball hits an arrow wheel, the ball will be sent in the direction that it is facing. Coins are also scattered throughout the area and can be collected with the ball, each coin adding 100 points to the score, albeit on a separate coin counter. Red Coins also appear alongside the other coins and are worth 1,000 points.
The layout of the coins and arrow wheels changes after each throw, regardless if it is a successful or a missed shot. The game is over when all ten basketballs are used up, and the player will receive a score based off of how many baskets they scored and how many coins they collected. The player can then choose to replay the game.
Coins collected in the game can be used on the official website to unlock characters, which can then be dragged on a field and selected to read snippets about each.