1d-1s-2n = 18-19. 1d-1s-3n = Solid 7-card minor with outside ace or king or two.

 

1d 1s 2N is a completely different auction than 1d 1N 2N. In the first case responder's bid is unlimited and forcing. In the second case responder's bid is limited and nonforcing.

 

In the first case you have a NT hand and fit it between the opening 1N 15-17 and opening 2N 20-21. Since responder is unlimited, you must "show points." In the second case, you may not have a good NT hand, but responder is offering a NT contract. If you agree to NT, your only consideration is how high. Since the 1N response limited responder's hand, opener has no need to "show points." You just do the math to decide the level.

 

If opener has 15 and responder has a max of 9, there is no game.Why would opener want to play in 2N instead of 1N?

 

If opener has 19 and responder has 6, there is game. Why would opener not want to play in 3N?

 

1N-2N always asks the same question regardless of the bidding that got you there. This is true for 1N-2N, 1D-1N-2N, and 1D-1S-1N-2N. "If you are max, bid 3N. If you are min, pass."

 

IMPORTANT BASIC RULE: Once a bidder makes a limiting bid, the other partner becomes the captain. ALL NT bids in the first two rounds are limiting. Whoever bids NT first, their partner is now the captain and chooses the final contract. Except in some slam bidding auctions, the NT bidder may only answer questions and may not take any unilateral action.