From the Super Mario Wiki
Shuffle Shell is one of Mario's minigames in Super Mario 64 DS. While gameplay is based on curling, the scoring is more reminiscent of archery, and the name is derived from yet another sport, shuffleboard.
In this minigame, the player must shoot Green Shells to the target found on the upper screen, using the blue paddle on the bottom of the Touch Screen with the stylus. Every time the player shoots a shell to the target, they will score points. The number of points will depend on the ring the shell is in when it stops moving; the blue ring gives 100 points, the pale ring grants 300, the red ring grants 500, and the center grants 1,000. If any shell does not touch the target, there will be no points. The user can shoot up to five Green Shells to the target, but the other shells stay in the field after being used. Knocking other shells will cause them to move around, which can change the points earned. Once the player has used all the shells in hand, the game ends. Sometimes the target may change its location in the upper screen when a new game starts. A minigame called Shell Smash has a similar concept to this minigame.
Use the paddle to push the Koopa shells to the target. The closer the shells land to the center of the target, the more points you will earn.
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