[foobar]

Assume that you are playing a limited opening system where 1M is 5+M unbalanced (unless 4M441). A 2♣ response shows a hand with less 3-card support that's least invitational but can't necessarily GF. It seems that there are several options for opener's rebid over the 2♣ response.

• 2♣ as optional relay to 2♦
  ........2♦: Waiting response with non-min hands
  ................2M: 2-card support, etc.
  ........2x: Min hands
  ........2N: 4441M?
  ........3m: ??
  
• 2♣
  ........2♦: Waiting response; may be GF with 6+M or min 4M441
  ...................2M: 2-card support
  ........2OM: Natural, F1
  ........2N: Max, 4M441
  ........3x: GF showing 5-4/5-5m

.
Any other suggestions? Note that invitational hands with 4+♠ might be an interesting corner case over 1♥.

[foobar]

 mycroft, on 2025-April-26, 10:56, said:

quick clarification: 5 unless 4M441?

Right, 5+M unbalanced unless 4M441.

[awm]

I think it would help to see the rest of the responses to 1M. Can 1♥-2♣ include four spades? Five spades? Can 1♠-2♣ contain five hearts? Are any other options available with a non-fitting invite (for example with a long diamond suit)?

[foobar]

awm, on 2025-April-26, 11:29, said:

I think it would help to see the rest of the responses to 1M. Can 1♥-2♣ include four spades? Five spades? Can 1♠-2♣ contain five hearts? Are any other options available with a non-fitting invite (for example with a long diamond suit)?

1M:
....1♠ (natural 4+, but probably < invite+)?
....1N: Currently defined as GFR, but best to also include 5+ invite with OM?
....2♣: Can have 4OM
....2♦ over 1♠: Currently defined as 6+♥, but unsure of what's best in terms of strength and follow-ups
....2M-1: Better raise of M, including some 3-card LRs
....2M: Raise
....2N: 4+ raise
....3x: Preemptive


2♣ can definitely have 4OM with invite+ hand, but it seems best to offload the 5+ invite with OM to 1N (taking a leaf out of your double-barreled invites here). On a side note, the response structure over 1M - 1N ® is structured to respond at 2N+ level with 4+ OM.

Over 1♠ - 2♦ is defined as 6+♥s (?), but it's unclear as to what the strength should be. Non fitting hands with long terms can conceivably bid 2♣, and then 3m over the 2♦ / 2M. Perhaps, it makes sense to have immediate 2M as a min hand for this reason.

Another interesting sequence is 1♥ - 1♠ - 1N, which is currently defined as showing 1=4=4=4. It's conceivably possible to flip that and 2♣, i.e., 1♥ - 1♠ - 1N shows 4+♣ and 1♥ - 1♠ - 2♣ shows 1=4=4=4. Of course, it likely requires removing hands invite+ hands with exactly 4♠ to allow responder to play in 2♦ instead for example.

[DavidKok]

Sorry, it's still not completely clear to me what responder's options are. It's been a while, or maybe this part of SCRUM has changed since I last looked at it. Let's stick with the 1♠ opening for now. I have heard of the Tarzan system before, which has some similarities. Their 1♠ opening is also limited and very similar (though it denies 4=1=4=4, and even denies 5=5=x=y, but it's close enough):

1♠-?

• Pass: Most hands with up to 8 points and no fit.
  
• 1NT: GFR, containing all hands with approximately (12)13+ HCP.
  
• 2♣: Exactly invitational. Defined through negative inferences: max 2♠, 4♥, optionally also max 5-5m.
  
• 2♦: Invitational(+), 5(+)♥, 2(-)♠.
  
• 2♥: Invitational, 3(+)♠.
  
• 2♠: Competitive, 3(+)♠.
  
• 2NT: J2NT.
  
• 3♣: Your choice. Some options include 'exactly invitational NF' (making 2♣ more tightly defined), 'weak' or 'artificial raise'.
  
• 3♦: Your choice. Some options include 'exactly invitational NF' (making 2♣ more tightly defined), 'weak' or 'artificial raise'.

If 1♠-3m is natural NF especially, the 1♠-2♣ is tightly defined. It shows around 10-12 HCP with at most 2 spades, 4 hearts, 5 diamonds and 5 clubs, and responder can narrow down the hand types and degree of support on the next round.

Is your 2♣ response similarly limited in both strength and shape? In the more complicated case of the 1♥ opening you also need to define which spades hand have priority - I think Tarzan uses 1♠ as GFR here and 1NT as 5(+)♠ (similar to KI5).

[mike777]

 foobar, on 2025-April-26, 09:42, said:

Assume that you are playing a limited opening system where 1M is 5+M unbalanced (unless 4M441). A 2♣ response shows a hand with less 3-card support that's least invitational but can't necessarily GF. It seems that there are several options for opener's rebid over the 2♣ response.

• 2♣ as optional relay to 2♦
  ........2♦: Waiting response with non-min hands
  ................2M: 2-card support, etc.
  ........2x: Min hands
  ........2N: 4441M?
  ........3m: ??
  
• 2♣
  ........2♦: Waiting response; may be GF with 6+M or min 4M441
  ...................2M: 2-card support
  ........2OM: Natural, F1
  ........2N: Max, 4M441
  ........3x: GF showing 5-4/5-5m

.
Any other suggestions? Note that invitational hands with 4+♠ might be an interesting corner case over 1♥.

What does 1M =5+ unbalanced mean?
What do you open with 5+balanced or semi balanced?

[foobar]

 mike777, on 2025-April-26, 16:56, said:

What does 1M =5+ unbalanced mean?
What do you open with 5+balanced or semi balanced?

5M332 opens 1♦ with 11-13 or 1N (14-16). 5M422 opens 1M or 1N.

[foobar]

 DavidKok, on 2025-April-26, 16:18, said:

Sorry, it's still not completely clear to me what responder's options are. It's been a while, or maybe this part of SCRUM has changed since I last looked at it. Let's stick with the 1♠ opening for now. I have heard of the Tarzan system before, which has some similarities. Their 1♠ opening is also limited and very similar (though it denies 4=1=4=4, and even denies 5=5=x=y, but it's close enough):

1♠-?

• Pass: Most hands with up to 8 points and no fit.
  
• 1NT: GFR, containing all hands with approximately (12)13+ HCP.
  
• 2♣: Exactly invitational. Defined through negative inferences: max 2♠, 4♥, optionally also max 5-5m.
  
• 2♦: Invitational(+), 5(+)♥, 2(-)♠.
  
• 2♥: Invitational, 3(+)♠.
  
• 2♠: Competitive, 3(+)♠.
  
• 2NT: J2NT.
  
• 3♣: Your choice. Some options include 'exactly invitational NF' (making 2♣ more tightly defined), 'weak' or 'artificial raise'.
  
• 3♦: Your choice. Some options include 'exactly invitational NF' (making 2♣ more tightly defined), 'weak' or 'artificial raise'.

If 1♠-3m is natural NF especially, the 1♠-2♣ is tightly defined. It shows around 10-12 HCP with at most 2 spades, 4 hearts, 5 diamonds and 5 clubs, and responder can narrow down the hand types and degree of support on the next round.

Is your 2♣ response similarly limited in both strength and shape? In the more complicated case of the 1♥ opening you also need to define which spades hand have priority - I think Tarzan uses 1♠ as GFR here and 1NT as 5(+)♠ (similar to KI5).

Yes, that's a good analogy. I am not sure of the need for KI over 1H, and it seems better to have a natural 1S response to cater to 4441. Starting the relay at 1N over 1M is more consistent, and removing the balanced hands resolves most shapes at +0 (except for the rare three-suiters, which are resolved higher).

Note that it's possible to include invite+ with 5OM in the 1N response (hoping to get out in 3M if necessary, or banking on the extra shape and 9+ fit to provide the oomph for game).

[awm]

It seems like you will want at least some minimums to bid 2♦ after 1M-2♣, since otherwise it's difficult to get out of the auction. Under this assumption, the structure of responder's rebids seems fairly clear. After 1♥-2♣-2♦ you probably want:

2♥ = doubleton heart
2♠ = 41xx or similar
2NT = 31(45) or 31(36) with a weak six card suit, or similar hands with heart void
3m = natural decent 6+ suit

Over these continuations, opener can remove 2nt to a 4+ minor (probably want this to be to play, since otherwise you have to play a lot of 8-9 card minor fits in 3nt). Over 2♥, opener is usually passing with a minimum, but should be able to remove with a minimum 4441. Over 3m, opener is usually passing with a minimum (maybe raising with 4-fit). I'd suggest that after 1♥-2♣-2♦-2NT you use 3M as showing the corresponding minor in a max hand, uncertain that 3nt is the best game.

It seems like the most problematic minimum hand is 4♠-5♥, where the sequence 1♥-2♣-2♦-2♥ could miss a spade fit, but you'd rather like to be playing 2♥ in the 5-2 when no spade fit exists.

For maximum hands, it seems like 5/5 can be a bit awkward, especially after 1♥-2♣-2♦-3♦ with the round suits or after 1♥-2♣-2♦-2♠ where you need a lot of bids to be NF. Also the various 4441 maximums might be awkward to describe after 1♥-2♣-2♦-2♥ (presuming 2♠/2NT are devoted to minimum 4441s).

Putting this together, you get something where:

1♥-2♣:
... 2♦ = minimums other than 4♠-5♥, or maximums without a lot of extra shape
... 2♥ = 4♠-5♥ minimum
... 2♠+ = some scheme for maximums with extra shape (including at least 5-5s) and max 4441 hands

Over 1♠-2♣ you have somewhat more room and therefore more flexibility, but I'd think the goal would be to make it as symmetric as possible with 1♥-2♣ for memory concerns.

[mw64ahw]

Tweaked from a version I developed for a 2♣ GI. Note I've include 3M where there is a choice of slams
1M-2♣
.. 2♦ Min, rejects game invite in ♦ <4oM
.... Pass Invitaional w. ♦
.... 2♥ <Shape?> as below
.... 3M 3M5+♣ choice of slams
.. 2♥ 4oM or over 1♠ GF 5♥
.. 2♠ 4+♣ max
.. 2N UB 6+M max
.... 3♣ <Shape?>
..... 3♦ 4m
....... 3♥ <minor?>
..... 3oM splinter
..... 3N ♣ splinter
..... 3M ♦ splinter
.. 3♣ 4+♦ max
.. 3♦ SB 6+M max
.. 3♥ over 1♠ GI 5♥
.. 3♠ over 1♥ 4522 max
.. 3M (semi)self-sustaining max
.. 3N 4441 max
.... 4♣ GF
.... 4X SI in X