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The game is very similar to Calvin and Hobbes's sport of the same name. You can never play it the same way twice in a row; players must make up rules as they go along. There is a big game each day; when the last match comes to an end, the players must come up with a new rule for use in the next game. They can add new rules in between matches as well.
After game hours, the Calvinball Supply Shop will open, and players can use Spiffiesthey've won in the last game to purchase new materials for future games.
There is also a spectator mode, which works like that in Super Smash Bros. 4. Players can bet Spiffies on who will win the current match or game.
There are several possible characters you can arrange into a team. They are classified by color to match their skill: