When play ends, the score is determined by comparing the number of tricks won by the declaring side to the number required to satisfy the contract. The available scoring points for the declaring side are dependent upon both the level and strain of the contract and are awarded to them only when the contract is 'made', i.e. at least the contracted for number of tricks are won by them. If the declaring side fails to take the required number of tricks, defending side receives points instead for "setting" (or "defeating") the contract. When the declarer makes the contract, the declarer's side receives points for: Every odd trick bid and made, known as contract points Each overtrick, i.e. each trick taken over the contract level, known as overtrick points Bonus points dependent upon the game variant being played for certain contract levels including part-game, game, rubber, small slam and grand slam contracts Bonus points in some game variants for making a doubled or redoubled contract Bonus points in some game variants for holding four or more honors in one hand When the declarer fails to make the contract, the defending pair receives points for undertricks the number of tricks by which declarer fell short of the goal. The various bonus structures give certain bid levels special significance. If the contract is made, the level of the contract is the primary factor affecting the scoring, rather than the number of tricks taken in play. For example, if the declarer takes all thirteen tricks in a notrump contract, there is a large score difference between contracts of 1NT and 7NT. This premium for contracting to take more tricks ensures competitiveness in the auction. Th

most important level is game, which is any contract whose bid trick value is 100 or more points. Game level varies by suit, since different suits are worth different amounts in scoring. The game level for notrump is three, the game level for hearts or spades (the major suits) is four, and the game level for clubs or diamonds (the minor suits) is five. See bridge scoring for details. Because of the value of the game bonus, much of the bidding revolves around investigating the possibility of making game. Even higher bonuses are also awarded for bidding and making small slam (level 6, i.e. 12 tricks) and grand slam (level 7, i.e. all 13 tricks) contracts. Even if a partnership holds most of the high cards and their opponents have no interest in bidding, they are still motivated to bid games and slams in order to achieve the best possible score, which in turn may result in a more challenging contract. While the scoring of individual hands in rubber and duplicate bridge share many features, the accumulation of scores over several hands differs significantlly. See bridge scoring for details. The concept of vulnerability affects scoring and introduces a wider range of tactics in bidding and play. Every partnership is in one two states: vulnerable or non-vulnerable, either by virtue of their previous deals in rubber bridge or as predetermined by the board in duplicate bridge. When a pair is vulnerable, game and slam bonuses are higher, as are penalties for failure to make the contract. Finally, doubling and redoubling also has a significant effect on scoring, especially for vulnerable contract which are either defeated or which win overtricks. See bridge scoring for details.