How 2 players games work...

[Phoxtrot]

This can be confusing because 2 players bridge isn't really a thing in real life and some of the choices made for the implementation in BGA are weird.

So let's explain how a round works.
(As much as possible, I'm using bridge terminology.)

Part 1 - Setup:

1. Both players receive a private normal hand of bridge of 13 cards.
2. There is also a revealed dummy that both players can see

Part 2 - Bidding:

1. Player 1 makes a bid (or pass)
2. Player 2 can now make an higher bid (or pass, or double if opponent had made a bid)
3. Bidding ends as soon as a player pass (unless we are talking of the very first action of the first player)
4. The player who made the last bid is the declarer

Part 3 - The Choice:

• Declarer must choose which dummy hand will be his partner : either the already "revealed dummy" or the "hidden dummy" (The hidden dummy being the one hand that no player has seen so far)

Part 4 - The Play:

1. The defense player sees his own dummy (the one not chosen by the declarer)
2. Defense player plays a card from his private hand or from his dummy. He doesn't get to choose from which one. I have not figured out yet how it is determined from which hand he must play from. Maybe you lead from your private hand if you made at least one bid ?
3. The declarer's dummy is revealed to the defense player (it was already visible to the declarer)
4. The defense's dummy is revealed to the declarer (it was already visible to the defense)
5. Both dummies remain revealed for the entirety of the play
6. Declarer plays a card from his dummy
7. Play continues with the usual bridge rules (except that there are 2 dummies instead of one that is)

Part 6 - Scoring

1. If imp is deactivated, your score is the raw score of the hand like you would have in a real bridge match (so it does give 50 points for a partial game). Unlike normal bridge matchs and competitions, your score is NOT compared to other people having played the same hand nor to an artificial "par" of the hand.
2. imp scoring : the raw score of the team with the most Honor points is compared to an artificial target score that depends on the honor points and vulnerability of the team. The difference is transformed into IMPs using a table (like in normal bridge). If the team with the most honor points scored more than the target score, it gains the IMPs, otherwise the other team does.

Part 5 - Some Notes:

1. Note that if the declarer's choose to play with the revealed dummy, the defense player with a tiny bit of memory can reconstruct all 4 hands in his head before he plays his first card
2. When bidding, you kind of have to decide already whether you want to play with the revealed dummy or the hidden hand... Bidding with the revealed dummy in mind as partner to then choose to play with the hidden one can be very risky.
3. Choosing to play with the hidden dummy is always at least a bit risky. An opponent bidding very low or not bidding at all is a clue that he has a weak hand which lets you deduce how strong the hidden hand should be but opponent could also have been seriously underbidding...
4. No matter what choice was made by the declarer, once a card has been played, each player can see 3 hands and therefore reconstruct the 4th hand as well in his head.
5. When playing with IMPs you can get screwed if the hidden hand was strong. So you may have to bid with the hidden hand in mind with all the dangers that implies...

[Phoxtrot]

Target Score :
(To be slowly filled...)

• 21 H : 50
• 29 H : 460 / 660
• 30 H : 490 / 690

When there are two numbers, the first is if you are not-vulnerable and the second is if you are vulnerable.

In a real bridge match, your target score is the score 2 other players in your team made with the exact same distribution of cards but with them playing with the cards that your opponents had at your table and your opponents' other team member played that hand with the cards that your team had at your table. So even with a very bad hand, you will get a positive difference if you did better that the other players did with your cards...

In other competitions, you might get compared to the score of multiple other team (separately) or against an average score or, rarely, against an artificial score (set in a more smart manner than in BGA)


The following table is presumably used when transforming difference between the row score and the target to IMPs :

Point difference IMPs
0-10 0
20-40 1
50-80 2
90-120 3
130-160 4
170-210 5
220-260 6
270-310 7
320-360 8
370-420 9
430-490 10
500-590 11
600-740 12
750-890 13
900-1090 14
1100-1290 15
1300-1490 16
1500-1740 17
1750-1990 18
2000-2240 19
2250-2490 20
2500-2990 21
3000-3490 22
3500-3990 23
4000 or more 24

In normal, real life, bridge a match will often be 24 or 32 hands
If just total the raw scores to determines the winner, a single very big hand can seal your fate with a big probability.
IMP scoring reduces the relative importance of big hands while still making a difference between hands where you had a result slightly bad and hands where you had a real bad result.

Here in BGA, the fact that the defense player can get tagged with a dummy hand that has a lot more value than expected but with a contract set by the opponent, gives IMPS an entirely different flavor and can induce bluffs in the bidding...
Still, it has one advantage compared to raw score : you lose points if you had enough honor points to normally score a game or slam and did not. In other words, having the best hands does not guarantee a win, you need to perform with them.

MP scoring is also popular in tournaments, look it up if you are interested. It's not implemented in BGA.