It plays a lot like Monopoly with buying and selling of stuff as you go around a board, only you have multiple pieces you get to move each turn and you'll get more pieces as the game progresses; but the main difference is that the person who is winning the game gets to decide what the rules for the game are each turn. As long as you are still winning once it becomes your turn again, you get to either make a new rule or amend another one.
your turn comes. You draw a card from the Rules Deck and then decide which players are effected by it. "Every time you roll the dice, collect $100 from the bank" - Oh, well, I think THAT rule should only apply to *me* and my little orange tokens on the board. "Every time you roll doubles, go to jail and skip your next turn". Yeah, that's gonna have to be something that affects the Red, Purple and Yellow tokens *only*.
Cards will also have simple "Gain three tokens and place them on the board", "Collect $50 from every player", "Loose $200" type cards, as well as complex game-changing "The Color with the most rules effecting them is now the "Winner", place as many tokens as needed in order to have one more token than anyone else on the board"
The way to win is to get 20 tokens on the board. The "Winning" person is the one with the most tokens on the board at the start of the current winner's turn each round.