Swapped 2♣♦
The positive responses 2♣♦ show 5+ cards in the other minor suit. They are game-forcing by unpassed hand like 2/1. This method helps finding minor suit slams. I spell out the minor suits because there is a subtle difference between them. Finding a big fit in clubs is easier because opener can have minimum long clubs.
Opener reverses with extra values to utilize higher steps to send information. This avoids an awkward situation Bridge World calls “two temporizers and zero describers.” Deviating from Polish Club 2020: Expert, I define 1♣-2♣♦-2♥♠ as reverses. This bidding structure separates 15–17 from the other ranges. I believe this treatment helps finding the best contract. When we only have a game, we want to play in a major suit despite of a better minor fit. However, we play the best fit in a slam to maximize our chances, especially at IMPs.
| 1♣-2♣- | FG, 5+♦ |
|---|---|
| 2♦! | NAT, 11–14 or 18+, 4+♦ |
| 2♥ | S/T, 18+, 5+♥ |
| 2♠ | S/T, 18+, 5+♠ |
| 2NT | NAT, 12–14 or 18+ |
| 3♣ | NAT, 11–14 or 18+, 6+♣ |
| 3♦ | S/T, 15+, 3+♦ |
| 3♥ | S/T, 15+, 4+♥, 5+♣ |
| 3♠ | S/T, 15+, 4+♠, 5+♣ |
| 3NT | COG, 15–17, 0–2♦ |
| 1♣-2♦- | FG, 5+♣ |
|---|---|
| 2♥ | S/T, 18+, 5+♥ |
| 2♠ | S/T, 18+, 5+♠ |
| 2NT | NAT, 12–14 or 18+ |
| 3♣ | NAT, 11–14 or 18+, 4+♣ |
| 3♦ | S/T, 18+, 6+♦ |
| 3♥ | S/T, 15+, 4+♥, 4+♣ |
| 3♠ | S/T, 15+, 4+♠, 4+♣ |
| 3NT! | COG, 15–17, 4+♣ |
I make 1♣-2♣♦-3NT so because otherwise it would be hard to show these hands. Grouping 11–14 and 18+ together is usually OK because 18+ can explore slams unilaterally.