[bridge] / convention.txt

* Executive summary:

Acol, 12-14 1NT, Weak twos, transfers, roman key card blackwood, Multi
Landy overcalls of 1NT

* Magic numbers:

Part score: 19-24 points
3NT / Major game: 25+
Minor game: 27+
Suit small slam: 31+
6NT: 33+
Suit grand slam: 35+
7NT: 37+

* General notes:
new suits often force for one round
jumps to game are usually "shut up"
"invitational to x" means bid x if maximal for previous bid
"support" is usually 4 cards (should add up to 8)
if you make a limit bid, you usually shut up unless forced

** Opening **

Opening points are 12, and/or rule of 20 (points + lengths of two
longest suits); 11 or 19 if you feel aggresive / it looks good

1 [suit] promises at least the above - generally pick the longest suit
1NT is 12-14 points balanced (limit)
2C is 23+ points. Usually game-forcing
2[other] 6-10 points, good 6-card suit (2 of A-Q, 3 of A-10)
2NT is 20-22 points balanced (limit)
3 [suit] pre-empt 7-card suit 7-9ish points
3NT pre-empt solid (AKQ at least) 7-card minor "Weak Gambling 3NT"
4 [suit] pre-empt as 3, but 8-card suit

A weak 2 denies a 4-card major or good 3-card major

(with 15-19 points balanced, open 1[suit] and rebid xNT - see below)

** Replying **

* Reponse to 1 [suit]

pass - <6 points
2 [suit] - support, 6-9 points (limit)
3 [suit] - support, 10-12 points (limit, invites game)
4 [suit] - pre-empt. 5+support, 6-10 points (to play)
xNT - denies support for partner (other responses do not)
1NT 6-9 points (doesn't need to be balanced), no 2-level bid (limit)
2NT 10-12 points, balanced (limit)
3NT 13-15 points, balanced (limit)
1 [new] 6+ points, 4+ cards, 1-round force
2 [new < suit] 8-9+ points, 5+ cards, 1-round force
jump [new] 16+ points, 5+ cards (or support), game force

* Response to 1NT

pass - <11 points, no long suit
2C - Stayman (bid 2 of a 4-card major or 2D if none)
2D/2H - Transfer (bid 2 of next suit)
2S - 11 points or long minor (bid 2NT if minimum, 3C if maximum)
2NT 12 points; invites game if opener maximal
3 [suit] - 5 cards in suit, forcing 1 round
 [in a minor, this is a thinking-about-slam bid, in a major, aiming
 for 3NT if you have 2 in the suit, 4[suit] with 3 or 4 cards]
4H/4S - 6-card suit. to play
3NT/6NT - to play
4NT - invitational to 6NT if maximum
5NT - invitational to 6NT unless minimum

* Response to 2NT

3C - Stayman (as before, but forcing to game)
3 [suit] - transfers (to a 5-card suit), game-forcing
others, as per 1NT

* Response to 2C (all game-forcing except 2C-2D-2NT (23-24 balanced))

2D - negative (<8 points)
Positive responses often suggest slam prospects
2NT - balanced, 8+ points, game-force
2 [suit] 5-card suit with an honour ~7+ points. game-force
3 [suit] decent 6-card suit. game-force

* Response to 2[suit] "RONF" (raise is the only non-forcing bid)

Raises are limits and opener must not bid again:
3 [suit] - 3/4 support 6-13 points
4 [suit] - 4/5 support 6-13 points (may be weaker with 5)

Other bids are forcing:
new suit - 16+ points 5+ cards, no support
2NT - 16+ points or 13+ points with 3+ support, opener shows a feature
(i.e. a stop) or rebids if none
3NT - 16+ points, stoppers in all other suits, signoff (likely to be a
tough contract, esp if communication bad)

* Response to pre-emptive 3
pass - <15 points, no support
4[suit] - 3+support
new suit (forcing) / game[suit] - 16+ points

** Rebidding **

* Rebidding after 1-level opening *

Minimum rebid own suit - 5+cards, 12-15 points
jump rebid own suit - 6+ cards, 15-19 points, very invitational

new suit < old suit - 12-15 points (old suit >= length new suit)
new suit > old suit [a reverse] - 16-19 points, 1-round force
 [first suit bid should be best suit when reversing]
jump new suit - 16-19 points, 1-round force

raise responder - 4+cards 12-15 points
single jump raise - 4+cards 16-18 points
game jump raise - 4+ cards 19 points

* NT rebids to show a balanced hand of 15-19 points *

[you opened 1[suit], and partner has replied at the 1-level]
1NT - 15-17 balanced (limit)
2NT - 18-19 balanced (limit)

[you opened 1[suit], and partner has replied at the 2-level]
2NT - 15-17 balanced (limit)
3NT - 18-19 balanced (limit)

** Later bids **

* 4th suit forcing *

The bid of the fourth suit at 2-level is forcing for one
round. Responder uses it where they lack a natural bid, but think the
partnership should go higher. It forces for one round, and opener bids
(in preference order):
raise responder's first suit with 3+support
NT with a stop in the fourth suit
raise the 4th suit with 4 cards in it
make the most natural rebid

* After the transfer *
e.g. after 1NT-1D-1H:

pass - weak hand
2NT - invitational to part-score or game in H or NT (shows 5 hearts)
3H - promises 6 hearts, invitational to game
new suit - promises 5-4 or 5-5, game-forcing
3NT - option to move to 4H or stay in 3NT
4H - promises 6 hearts, to play

* After a 1NT-2S transfer *

opener bids 2NT if minimum:
pass or bid a minor suit

opener bids 3C if maximum:
pass, bid 3D, or 3NT

** Slamming :-) **

*Roman Key Card Blackwood*

4NT once a suit has been agreed asks for the 5 key cards (trump K +
aces):
5C: 0/3 key cards
5D: 1/4 key cards 
5H: 2/5 key cards no trump Q
5S: 2/5 key cards with trump Q

*Cue bids*

These are a bit advanced, so we might not want to bother, but. Once a
suit has been agreed explicitly or implicitly (e.g. 1NT-3S) and you're
thinking about slam, bid of a side-suit shows first-round control of
that suit, which might be a void. A return by either partner to the
trump suit is often an end to the process

e.g. 1NT-3S-4D shows the first bidder to have 1st-round control in
Diamonds (and no such control in clubs); you can continue on to
2nd-round controls if you like.

** Overcalls **

Against a 1-level bid, 1NT shows 16-18 points and a stop in the bid
suit (you may bid stayman on top if relevant), unless in fourth place
where it is 12-14 as normal e.g. 1H-p-p-1NT or p-p-1H-1NT.
With more points, double, then bid NT next time.

1[suit] overcall is 5+cards, 8-16ish points
2[suit] overcall is 6+cards, 12-15ish points
a game overcall in a major with 6+cards 17+ points can be worth a shot

** Overcalls of 1NT **

Pass - <9 points
Double - 15+ points (for penalties) [or 19+ facing strong 1NT]

(the following bids are all alertable)
2C    - 5-4 or 5-5 in the majors
2D    - a 6-card major with no side suit
2H/S  - 5 H/S, 4+ in a minor
2NT   - at least 5-5 in the minors
3C/3D - 10-15 points, good 6+ card suit
3H/3S - 7+ cards, 5-9 points, pre-empt

* Response to 2C (which showed 5-4/5-5 majors)
Pass  - 6+ clubs (non-forcing)
2D    - equal length in majors
2H/2S - sign-off preference for H/S
2NT   - 12-14 balanced (natural, non-forcing)
3C    - 15+ game-force, artificial
3D    - 6+ diamonds, 10-14 points
3H/3S - invitational in H/S

* Response to 2D (showed a 6-card major)
Pass  - 6+ diamonds(!)
2H    - sign-off in H OR invitational in S (3S over 2S correction)
2S    - sign-off in S OR game-going in H (4H over 3H correction)
2NT   - artificial, game-going [see below]

* Response to 2H/2S (showed a 5-card major, 4+ minor)
Pass     - 2/3 of the bid suit (and no 4+ minor)
2NT      - artificial, please bid your minor suit
3NT      - to play
3[suit]  - support, invitational to game
4[suit]  - support, to play
new suit - denies support, 6+ cards (or 5+ if 2S)

* Response to 2NT (showed at least 5-5 minors)
3C       - to play
3D       - to play (denies club support)
3H/3S    - 6+ in that suit, no minor support
3NT      - to play
4C/4D    - 3+ support, invitational
4H/4S    - to play

* Continuation of 2D-2NT sequence:
3C    - Hearts, maximal
3D    - Spades, maximal
3H    - Hearts, minimum
3S    - Spades, minimum

** Doubles **

Takeout double needs about 13 points, shortage in the opponents suit.
Double then bid suggests more like 17+ points
Double then jump suggests a killer 21+ point hand

A takeout double is forcing unless you are very strong in the bid
suit:
pass [!!] 8+ points, good in trumps, requesting trump lead
suit - your best suit
jump-suit - 8+ points
1NT - 8-11, stop in bid suit
2NT - 12-13, stop in bid suit
3NT - 14+, stop in bid suit

A low-level double when the doubler's partner has passed is nearly
always a takeout.
"A double of a suit call below the four level is for takeout when made
at the player's first opportunity of doubling, providing that the
doubler's partner has not bid"
NT doubles are always penalty
doubles of suit escapes from doubled NT are always penalty
doubles of openings up to 3[suit] are usually takeouts
doubles of overcalls up to 2S are usually takeouts

** Defences to overcalls of 1NT **

* Defence to a Natural 2C overcall
Dble  - Stayman
otherwise, like response to 1NT

* Defence to other natural overcalls
Dble for penalties, other bids natural

* Defences to Multi-Landy bids
(i.e. what to do when partner's 1NT is overcalled thus)

Generally, pass unless you have roughly invitational values (so
11ish); other bids are natural except:

Against 2C overcall (5-4/5-5 majors):
Dble   - I can penalize at least one of the majors
3C     - Natural and forcing

Against 2D overcall (6-card major):
Dble   - Stayman
3D     - Natural and forcing

Against 2H/2S (5-card major, 4+ minor):
dble    - Penalties in the bid suit
3[suit] - Game-forcing Stayman

Against 2NT (at least 5-5 minors):
dble    - I can penalize at least one of the minors
3C      - Stayman, not game forcing
3D      - Stayman, game forcing
3H/S    - natural, game forcing