升级（拖拉机）与 找朋友 —— 一类流行于中国的接牌游戏的在线玩法说明。 Tractor and Finding Friends — a guide to the popular Chinese trick-taking card game played on this site. The base rules below apply to Tractor; the highlighted "Finding Friends only" callout marks the extra rules that apply to the Finding Friends variant.
Ben Zhang has written another introduction here that might also be worth reading. Ben Zhang 还写了一篇介绍，见 这里，也值得一读。
Tractor is a family of trick-taking card games popular in China. It's also known as tractor, 40 points, 80 points, playing for 100 points, finding friends, among others. You can play online here. 升级 是一类流行于中国的接牌游戏，又称 拖拉机、四十分、八十分、打百分、找朋友 等。你可以在此在线游玩。
This online implementation uses a fairly standard rule set. There are a wide variety of house rules that aren't implemented; but could be — feel free to propose new functionality on GitHub. 本在线实现使用一套相当标准的规则。还有很多家庭规则尚未实现，但都可以加入——欢迎在 GitHub 上提出新的功能建议。
There are 54 cards per deck (13 cards per suit, plus a small joker and a big joker). Aces (A) are treated as higher-valued than Kings (K). Usually, a deck is added for every two players in the game (so 4 players and 5 players play with 2 decks, but 6 players play with 3). 每副牌有 54 张（每门花色 13 张，外加一张小王和一张大王）。A 比 K 大。通常每两名玩家增加一副牌（因此 4 人和 5 人用 2 副牌，6 人用 3 副牌）。
Kings, tens, and fives are valuable cards and have point values. Kings and tens are worth ten points each. Fives are worth five points each. K、10 和 5 是分牌，具有分值。K 和 10 每张值 10 分，5 每张值 5 分。
The two jokers are ordered, with the uncolored joker having a lower value than the colored joker. 两张王有顺序：小王（黑白）小于大王（彩色）。
Scoring in each round of the game is determined by "point" cards. Only fives, tens, and kings have points — all other cards do not count for scoring. Point scores are pooled within a team. 每局的得分由“分牌”决定。只有 5、10 和 K 有分，其余牌不计分。分数在队伍内汇总。
| Card number牌面 | Point value分值 |
| 5 | 5 |
| 10 | 10 |
| K | 10 |
Each deck has a total of 100 points (25 per suit). However, as cards of the trump rank are part of the trump suit, the trump suit will have a disproportionately large number of points when the trump rank is 5, 10, or K. 每副牌共 100 分（每门花色 25 分）。但由于级牌属于主牌花色，当级牌为 5、10 或 K 时，主牌花色的分数会异常地多。
Each player in the game has a rank, starting at 2 and going to A. If they win rounds, their rank may increase. The rank of the leading player for a round determines the trump rank for that round. 每名玩家都有一个级别，从 2 开始一直到 A。赢得局后级别可能上升。某局庄家的级别决定了该局的级牌。
The game ends when a player successfully defends a round at the A rank. 当某名玩家在 A 级别成功守庄后，游戏结束。
In each round, there is a trump specification which determines what cards are part of the trump suit. The trump specification always includes a trump rank, but doesn't necessarily include a specific suit. Jokers are always a part of the trump suit. 每局都有一个主牌设定，决定哪些牌属于主牌花色。主牌设定一定包含级牌，但不一定指定具体花色。王始终属于主牌花色。
For example, if the trump rank is 4 and the specified suit is spades (♤), the trump suit consists of all 4s, all jokers, and all spades. A card can only be a part of one suit, so the 4♡ is no longer considered to be a member of the hearts (♡) suit. 例如，若级牌为 4 且指定花色为黑桃（♤），则主牌花色由所有 4、所有王和所有黑桃组成。一张牌只能属于一门花色，因此 4♡ 不再属于红桃（♡）花色。
In all suits, the 3 and the 5 are now considered to be adjacent. 在所有花色中，3 和 5 现在被视为相邻。
The order of the trump suit is as follows (highest to lowest): 主牌花色的顺序如下（从高到低）：
In the case of the trump specification of 4♤, the ordering from highest to lowest is当主牌设定为 4♤ 时，从高到低的顺序为 big joker > small joker > 4♤ > [ 4♡ = 4♢ = 4♧ ] > A♤ > K♤ > Q♤ > J♤ > 10♤ > 9♤ > 8♤ > 7♤ > 6♤ > 5♤ > 3♤ > 2♤.
If only a trump rank is specified (and no suit), the only trumps are cards of the trump rank, and jokers. This is referred to as "no trump", and there are five distinct suits (as opposed to the usual four). 若只指定级牌（不指定花色），则主牌只有级牌和王。这称为“无主”，此时有五门不同的花色（而非通常的四门）。
In all suits, the 3 and the 5 are now considered to be adjacent. 在所有花色中，3 和 5 现在被视为相邻。
The order of the trump suit is as follows:主牌花色的顺序如下：
In the case of the trump specification of 4NT, the ordering from highest to lowest is当主牌设定为 4 无主时，从高到低的顺序为 big joker > small joker > [ 4♤ = 4♡ = 4♢ = 4♧ ].
There are two fundamental teams in the game: one team is trying to acquire points, while the other team is trying to discard them. Colloquially, the team trying to acquire points is "attacking", and the other team is "defending". 游戏中有两个基本队伍：一队设法获取分数，另一队设法甩掉分数。通常，争取分数的一队称为“进攻方”，另一队称为“防守方”。
The defending team is determined by a designated leader of the team (the declarer). In Tractor, the teams are fixed and the leader rotates among the winning team. In Finding Friends, the leader rotates among the team that won the previous round, but the teams are fluid and change from round-to-round. 防守方由该队的指定庄家（当庄）决定。在 升级 中，队伍固定，庄家在获胜队伍内轮换。在 找朋友 中，庄家在上局获胜的一方内轮换，但队伍是流动的，每局都会变化。
The leader (whoever is the declarer) of the team gets an additional advantage at the beginning of the game: they can see the extra "bottom cards" (the bottom) and exchange them for cards in their hand. Otherwise, all players are the same, and teams only matter for scoring. 庄家（当庄）在开局时有一项额外优势：他们可以看到额外的“底牌”，并用手牌进行交换。除此之外，所有玩家都一样，队伍只在计分时起作用。
The game begins by players drawing cards one at a time. Like most Chinese card games, cards are drawn in counter-clockwise order. 游戏开始时，玩家逐张摸牌。与大多数中国纸牌游戏一样，摸牌按逆时针顺序进行。
At any point, a player may "bid" for the trump by showing valid bids out of their hand. The highest bid determines the trump specification for the game. However, once a player has made a bid, they can only "reinforce" it by adding more of the same card, or wait for another player to displace them as the highest bidder. 任何时候，玩家都可以亮出手牌中合法的叫牌来“叫主”。最高的叫牌决定该局的主牌设定。但玩家一旦叫牌，就只能通过加亮更多相同的牌来“加固”，或等待其他玩家把自己挤下最高叫牌的位置。
Valid bids must be made up of identical cards (i.e. same card-face). The bids can be either cards of the current trump rank or jokers. The current trump rank corresponds to the rank of the leader of the defending team. Each game starts with all players at rank 2. Joker bids represent "no trump" bids. A single joker cannot be used as a bid. 合法的叫牌必须由相同的牌组成（即同一张牌面）。叫牌可以是当前级牌的牌或王。当前级牌对应防守方庄家的级别。每局开始时所有玩家都在 2 级。王的叫牌代表“无主”叫牌。单张王不能用于叫牌。
Each bid made must be greater than all of the previous bids. This is determined first by the number of cards (more is higher), and then by card values (following the "no trump" ordering of card values). 每次叫牌都必须高于之前所有的叫牌。先比较张数（多者为高），再比较牌的大小（按“无主”的牌值顺序）。
The final trump specification is determined by the winning bid. If the winning bid is made up of jokers, the trump specification is "no trump"; otherwise, it is the suit of the winning bid. All cards in this suit and jokers are considered trumps. 最终的主牌设定由获胜的叫牌决定。若获胜叫牌由王组成，则主牌设定为“无主”；否则为获胜叫牌的花色。该花色的所有牌以及王都被视为主牌。
Example with trump rank of 2:级牌为 2 的示例：
Result: 2NT trump specification, player 1 wins the bid.结果：2 无主的主牌设定，玩家 1 获得叫牌。
If this is the first round being played, the winner of the bid is also the leader of the defending team (the declarer). Otherwise, the only consequence of the bidding process is setting the trump specification. 如果这是第一局，叫牌获胜者也是防守方的庄家（当庄）。否则，叫牌过程的唯一作用就是确定主牌设定。
After the drawing phase is completed, 4 to 8 cards are left in the bottom of the draw pile and become the bottom cards. For example, in a four-player game, there will be 8 cards left; in a five-player game, there will be 6. These cards are made available for the leader of the defending team (the declarer) to pick up. 摸牌阶段结束后，牌堆底部会剩下 4 到 8 张牌，成为底牌。例如，四人局会剩 8 张，五人局会剩 6 张。这些牌供防守方庄家（当庄）拿取。
The leader may choose to swap some, all, or none of the cards in the bottom for cards in their hand. The number of cards in the bottom must remain constant. 庄家可以选择用手牌交换底牌中的部分、全部或不交换任何牌。底牌的张数必须保持不变。
There is a potential penalty for hiding points in the bottom, since other players can't see them. This is surfaced as a multiplier on the number of points left in the bottom, which are treated as if they are attached to the last trick in the game. 把分藏在底牌里有潜在的惩罚，因为其他玩家看不到。这体现为底牌中剩余分数的一个倍数，并被视为附加在游戏最后一轮上。
| Length of the last trick-format最后一轮牌型的长度 | Point multiplier分数倍数 |
| 1 | 2 |
| 2 (e.g. pair)（如对子） | 4 |
| 3 (e.g. triple)（如三张） | 6 |
| 4 (e.g. tractor)（如拖拉机） | 8 |
The multiplier can be generalized to arbitrarily large trick-formats. In the case of the last trick-format being a "throw", or a set of the highest possible individual trick-formats, the length of the longest trick-format within the group should be used for the multiplier. 该倍数可推广到任意大的牌型。若最后一轮的牌型是“甩牌”，即一组各花色中最高的单个牌型，则应使用该组中最长牌型的长度来计算倍数。
In addition to exchanging cards with the bottom of the deck, in games of Finding Friends, the leader also specifies which cards identify their "friends" (i.e. members of the defending team). These must be committed to at the beginning of the game, and the leader is allowed to become their own friend (intentionally or unintentionally). 在 找朋友 中，除了与底牌交换外，庄家还要指定哪些牌用来确认其“朋友”（即防守方的成员）。这些必须在开局时确定，且庄家可以成为自己的朋友（有意或无意）。
The number of friends is determined by the number of players — the defending team should never be larger than the attacking team. 朋友的数量由玩家人数决定——防守方绝不应大于进攻方。
A friend is declared as a combination of a specific card (suit/number) and an ordinal. For example, one could declare that the "first person to play an A♤" is their friend. They could also declare that the third person to play the card is their friend. 朋友以“一张具体的牌（花色/点数）+ 一个序数”来宣布。例如，可以宣布“第一个打出 A♤ 的人”是自己的朋友，也可以宣布第三个打出该牌的人是朋友。
Cards above the value of A cannot be declared as friends. That is, cards of the trump rank and jokers are not legal friend cards. 大于 A 的牌不能宣布为朋友。也就是说，级牌和王都不是合法的朋友牌。
In many cases, this results in the leader and the other players not knowing who the friends are. Once a trick has been completed in which a person has played the friend card, they join the defending team and bring their points with them. 很多情况下，这会导致庄家和其他玩家都不知道谁是朋友。一旦某人打出朋友牌的那一轮结束，他们就加入防守方，并带着自己的分数一起加入。
All cards in a trick format must be in the same suit. Any winning play (whether it is setting the format or not) must be made up of a single suit; that suit will match either the initial format or be made up of trumps. 一个牌型中的所有牌必须同花色。任何获胜的出牌（无论是否设定牌型）都必须由单一花色组成；该花色要么与初始牌型一致，要么由主牌组成。
There are three basic trick formats in the game: single cards, identical cards, and sequences of identical cards. A set of the highest possible plays in a single suit can be played simultaneously as a "throw", which makes it potentially harder to trump. 游戏中有三种基本牌型：单张、相同的牌、以及相同牌的连续序列。某一花色中一组最高的牌可以同时打出作为“甩牌”，这可能会更难被吃掉。
In general, players must attempt to match the format to the best of their ability using cards in the same suit. If the player has no remaining cards in the suit (i.e. they are void in the suit), there are no requirements on what cards they can play. 一般来说，玩家必须尽力用同花色的牌去匹配牌型。如果某花色已无剩牌（即在该花色缺门），则对其出什么牌没有要求。
Any single card can always lead a trick. Other players are required to play a card in the same suit if they have one; otherwise, any card can be played. 任何单张都可以领出一轮。其他玩家若有同花色的牌则必须出，否则可以出任意牌。
If a trump card is played, the highest trump card wins the trick. Otherwise, the highest card in the original suit wins the trick. If the same card is played by multiple players, the first one to play has precedence. 若有主牌打出，则最大的主牌赢得该轮。否则，原花色中最大的牌赢得该轮。若多名玩家打出相同的牌，先打者优先。
Example:示例：
Player 3 wins this trick, because they played the highest card in the same suit (A♤) first. 玩家 3 赢得这一轮，因为他们最先打出了同花色中最大的牌（A♤）。
Example 2:示例 2：
Player 2 wins this trick, because they played the highest trump card (big joker). Note that Player 3 is also void in spades (♤), but did not play a trump card and so cannot win the trick. 玩家 2 赢得这一轮，因为他们打出了最大的主牌（大王）。注意玩家 3 同样在黑桃（♤）上缺门，但没有打出主牌，因此不能赢得该轮。
Sets of identical cards can always lead a trick. Other players are obligated to match the set as best they can within the suit. 相同牌的组合都可以领出一轮。其他玩家有义务在该花色内尽量匹配。
Note: cards of equal value are not necessarily identical; they have to have the exact same card face. 注意：等值的牌不一定相同；它们必须是完全相同的牌面。
Examples:示例：
For example, if the trick-format is triples, the ordering of required plays is:例如，若牌型是三张，则要求出牌的优先顺序为：
Only plays which match the trick-format (either in the original suit, or in trump) are eligible to win the trick. As with the single-card format, the first player to play an identical play has precedence. 只有匹配牌型的出牌（无论在原花色还是主牌中）才有资格赢得该轮。与单张牌型一样，先打出相同牌型者优先。
Example:示例：
Player 4 wins this trick, because they played the highest pair in the same suit (3♤3♤). Player 2 and Player 3 did not play a pair; therefore, they cannot win this trick, and (by inference) cannot have any spade pairs remaining in their hands. 玩家 4 赢得这一轮，因为他们打出了同花色中最大的对子（3♤3♤）。玩家 2 和玩家 3 没有打出对子；因此他们不能赢得该轮，并且（可以推断）手中不再有黑桃对子。
Example 2:示例 2：
Player 3 wins this trick, because they played a trump pair. Because both Player 2 and Player 3 played non-spade cards, they must be void in spades. 玩家 3 赢得这一轮，因为他们打出了一对主牌。由于玩家 2 和玩家 3 都打出了非黑桃的牌，他们一定在黑桃上缺门。
Consecutive sequences of at least two identical cards of the same size and in the same suit are called tractors, and are a special play-type in and of themselves. They are parameterized by their length and the number of identical cards, both of which are required to be at least two (the smallest tractor is four cards). 同花色、同张数且至少有两组连续的相同牌，称为拖拉机，本身是一种特殊牌型。它们由长度和相同牌的张数两个参数确定，二者都至少为 2（最小的拖拉机是四张牌）。
Examples:示例：
Whether pairs are sequential depends on the current trump: since cards with the trump rank are some of the highest trumps, right below the jokers, their positioning in the overall order has changed. 对子是否连续取决于当前的主牌：由于级牌是仅次于王的最高主牌之一，它们在整体顺序中的位置发生了变化。
Example of sequential pairs due to trump-number reordering:因级牌重排而连续的对子示例：
Additionally, pairs of equal cards don't make tractors.此外，等值牌的对子不能组成拖拉机。
Tractors are relatively uncommon, and tend to win tricks. They are also strategically good, because matching the tractor format is at least as difficult as matching the equivalent number of identical cards. 拖拉机相对少见，往往能赢得该轮。它们在策略上也很有利，因为匹配拖拉机牌型至少和匹配同等数量的相同牌一样困难。
For example, if the trick-format is tractors made up of three consecutive pairs, the ordering of required plays is:例如，若牌型是由三组连续对子组成的拖拉机，则要求出牌的优先顺序为：
Only plays which match the trick-format (either in the original suit, or in trump) are eligible to win the trick. As with the single-card and identical-card formats, the first player to play an identical play has precedence. 只有匹配牌型的出牌（无论在原花色还是主牌中）才有资格赢得该轮。与单张和相同牌牌型一样，先打出相同牌型者优先。
Example:示例：
Player 1 wins this trick, because they are the only player to meet the format. Player 2 and Player 3 played non-consecutive pairs, while Player 4 played cards in a different suit. Since this trick is led with a tractor, all players had to play two pairs in spades if they had them. 玩家 1 赢得这一轮，因为只有他们符合牌型。玩家 2 和玩家 3 打的是不连续的对子，而玩家 4 出的是不同花色的牌。由于这一轮以拖拉机领出，所有玩家若有黑桃的两对就必须打出。
Any set of the highest possible trick-formats in a given suit can be played simultaneously as a "throw". It is expected that the player initiating a throw believes that their play is valid, i.e. that no other player can defeat any component of the throw using cards in the same suit. 某一花色中一组最高的牌型可以同时打出作为“甩牌”。发起甩牌的玩家应当相信自己的出牌是有效的，即没有其他玩家能用同花色的牌击败该甩牌的任何组成部分。
Once a throw has been played, each player should (in counter-clockwise order) affirm that the throw is valid and that it cannot be defeated within the same suit. If the throw is determined to be invalid, the player which initiated the throw is obligated to lead with the component that can be defeated. In this implementation, no additional penalties are imposed on incorrect throws. 甩牌打出后，每名玩家应（按逆时针顺序）确认该甩牌有效且在同花色内无法被击败。若判定甩牌无效，则发起甩牌的玩家必须改为领出可被击败的那一部分。在本实现中，错误的甩牌不会受到额外惩罚。
Other players are not obligated to ensure that their plays are the highest possible plays within their own suits, though they still need to match each component's trick-format as best they can within the suit. 其他玩家无需确保自己的出牌是其花色中最高的，但仍需在花色内尽量匹配每个组成部分的牌型。
Examples for two decks:两副牌的示例：
In cases of ambiguity between components (e.g. five-of-a-kind vs. tractor), the interpretation with the longest single component is chosen. If there are multiple ambiguous components of the same length, tractors are preferred over identical cards. 当各组成部分存在歧义时（如五张 vs. 拖拉机），选择单个组成部分最长的解释。若有多个等长的歧义部分，则拖拉机优先于相同牌。
Example of a throw ambiguity:甩牌歧义示例：
The above play can be interpreted as either a tractor and a single card ([2♤2♤3♤3♤] + 2♤), or as a triple and a pair ([2♤2♤2♤] + [3♤3♤]). Since the former interpretation has a maximum component length of 4 cards, greater than the latter's 3 cards, we interpret this as a tractor and a single card. The "full house" concept from poker does not exist in this game. 上面的出牌既可解释为一个拖拉机加一张单牌（[2♤2♤3♤3♤] + 2♤），也可解释为一个三张加一对（[2♤2♤2♤] + [3♤3♤]）。由于前一种解释的最大组成部分为 4 张，大于后者的 3 张，因此我们将其解释为拖拉机加一张单牌。扑克中的“葫芦”概念在本游戏中不存在。
Only plays which match the trick-format (either in the original suit, or in trump) are eligible to win the trick. As with the other formats, the first player to play an identical play has precedence. 只有匹配牌型的出牌（无论在原花色还是主牌中）才有资格赢得该轮。与其他牌型一样，先打出相同牌型者优先。
Note: in order to defeat a throw, every component of the throw must be individually defeated. Since a throw is only valid if it cannot be defeated within its own suit, this means that a throw can only be defeated by the same pattern of cards in the trump suit. 注意：要击败甩牌，必须分别击败其每一个组成部分。由于甩牌只有在同花色内无法被击败时才有效，这意味着甩牌只能被主牌花色中相同形态的牌击败。
Example:示例：
Player 1 wins this trick, because they are the only player to meet the format. Note: though there exists another pair of Q♤Q♤ played by Player 2, this is a valid throw because no player can show that they have K♤K♤ or A♤A♤, which are the only two higher pairs. Player 3 is particularly upset, here, because they had a tractor in spades, but it can't win in a trick with a two-pair-throw format. Since this trick is led with a throw of two pairs, all players had to play two pairs in spades if they had them. 玩家 1 赢得这一轮，因为只有他们符合牌型。注意：尽管玩家 2 打出了另一对 Q♤Q♤，但这仍是有效的甩牌，因为没有玩家能证明自己手中有 K♤K♤ 或 A♤A♤，而这是仅有的两对更高的对子。玩家 3 尤其郁闷，因为他们手里有黑桃的拖拉机，但在两对甩牌的牌型里它赢不了。由于这一轮以两对的甩牌领出，所有玩家若有黑桃的两对就必须打出。
Example 2: trump is 2♢示例 2：主牌为 2♢
Player 2 wins this trick (admittedly contrived): both Player 2 and Player 3 played trump cards in the appropriate format. However, though Player 3's pair of 4♢4♢ is higher than Player 2's 3♢3♢, their 6♢ is not higher than Player 2's 8♢, so Player 2 takes precedence. 玩家 2 赢得这一轮（不得不说有点刻意）：玩家 2 和玩家 3 都按相应的牌型打出了主牌。然而，尽管玩家 3 的一对 4♢4♢ 高于玩家 2 的 3♢3♢，他们的 6♢ 并不高于玩家 2 的 8♢，因此玩家 2 优先。
In each trick, the first cards (also known as the lead cards) denote the format of the trick. Only plays which match the trick's format are eligible to win the trick. 每一轮中，最先出的牌（也称领出牌）确定该轮的牌型。只有匹配该轮牌型的出牌才有资格赢得该轮。
Every player contributes the same number of cards to each trick. Therefore, every player runs out of cards at the same time. 每名玩家在每一轮中出相同数量的牌。因此，所有玩家同时出完手牌。
Players are also obligated to match the trick format to the fullest extent possible: if they are able to match the format within trick's suit, they must play those cards. If they can't match the format but can match a looser variant of the format (e.g. they have a pair in the suit, but the format requires a triple), they are also obligated to play those cards. 玩家还有义务尽最大可能匹配牌型：若能在该轮花色内匹配牌型，就必须打出这些牌。若无法匹配牌型但能匹配较宽松的变体（如该花色有一对，而牌型要求三张），也必须打出这些牌。
This implies that a player can only play cards of a different suit than the leading play in a trick if they have no cards in that suit (i.e. they are void in the suit). 这意味着，只有当玩家在领出花色上无牌（即缺门）时，才能在该轮出不同花色的牌。
The winner of the current trick will play the first cards (and set the trick format) for the next trick. 本轮的赢家将领出下一轮的牌（并设定下一轮的牌型）。
The winning team for each round is determined by the number of points the opposing team earned from tricks. If the opposing team won the last trick, the cards hidden in the bottom are revealed. The point value of any valuable cards at the bottom are multiplied by twice the number of cards in the largest component of the last trick's format and awarded to the opposing team. 每局的获胜队伍由对方从各轮中获得的分数决定。若对方赢得了最后一轮，则揭开底牌。底牌中分牌的分值会乘以最后一轮牌型中最大组成部分张数的两倍，并判给对方。
There are five possible outcomes depending on the number of decks, as detailed in the following table:根据牌副数，有五种可能的结果，详见下表：
| Opposing team's points对方的分数 | Result结果 |
| 0 | Defending team wins and goes up three levels防守方获胜，升三级 |
| 5 to n-5 | Defending team wins and goes up two levels防守方获胜，升两级 |
| n to 2n-5 | Defending team wins and goes up one level防守方获胜，升一级 |
| 2n to 3n-5 | Opposing team wins, but keeps the same level对方获胜，但级别不变 |
| 3n to 4n-5 | Opposing team wins and goes up one level对方获胜，升一级 |
| 4n to 5n-5 | Opposing team wins and goes up two levels对方获胜，升两级 |
| 5n and above | Opposing team wins and goes up three levels对方获胜，升三级 |
The winning team becomes the defending team in the next round, and the next person counter-clockwise from the current leader is the leader for the next round. 获胜队伍成为下一局的防守方，当前庄家逆时针方向的下一个人成为下一局的庄家。
The winner of the game is the person who gets to the highest possible rank and successfully defends it first. In this implementation, this is A. 游戏的赢家是最先到达最高级别并成功守庄的人。在本实现中，最高级别为 A。