Online casino games are designed to favor the house, ensuring that over the long term, the casino will make a profit. For example, roulette wheels include a zero (or double zero in American roulette) to give the house an edge. Slot machines are programmed to return a certain percentage of money to players, but not enough to cause a loss for the casino. While the games are not 'rigged' in the sense that they are dishonest, they are mathematically designed to ensure that the casino has a statistical advantage over players.