Game-forcing 2♣♦

The positive responses 2♣♦ show a longest suit with 5+ cards. 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 12–14 with a 4-card major. 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♦!S/T (R), 15+, 4+♣
2♥S/T, 15+, 4+♥
2♠S/T, 15+, 4+♠
2NTNearly BAL, 12–14 or 18+
3♣NAT, 12–14 or 18+, 4+♣
3♦S/T, 18+, 6+♦
3♥S/T, 18+, 6+♥
3♠S/T, 18+, 6+♠
3NTNAT, 12–14, 3343
1♣-2♦-FG, 5+♦
2♥S/T, 15+, 4+♥
2♠S/T, 15+, 4+♠
2NTNearly BAL, 12–14 or 18+
3♣NAT, 12–14 or 18+, 5+♣
3♦S/T, 15+, 4+♦
3♥S/T, 18+, 6+♥
3♠S/T, 18+, 6+♠
3NT!S/T, 15–17, 5+♣

I make 1♣-2♦-3NT so because otherwise it would be hard to show these hands. Grouping 12–14 and 18+ together is usually OK because 18+ can explore slams unilaterally.

By passed hand

P-1♣-2♣♦ reduce to natural invitations without a 4-card major. Opener hides 4-card majors in this case.

There is still an important difference between 2♣ and 2♦. Opener can always sign off by passing 2♣ due to a sure 7-card club fit. This is not the case for 2♦.

P-1♣-2♣-INV, 5+♣
2♦S/T, 4+♦
2♥S/T, 5+♥
2♠S/T, 5+♠
2NTBAL S/T
3♣S/T, 4+♣
3♦S/T, 6+♦
3♥S/T, 7+♥
3♠S/T, 7+♠
P-1♣-2♦-INV, 5+♦
2♥S/T, 5+♥
2♠S/T, 5+♠
2NTTo play
3♣To play, 6+♣
3♦S/T, 3+♦
3♥S/T SPL, 0–1♥, 5+♣
3♠S/T SPL, 0–1♠, 5+♣
3NTTo play
4♣S/T, S-SOL 6+♣
4♦S/T, UNBAL 4+♦
4♥S/T, SOL 7+♥
4♠S/T, SOL 7+♠
4NTQUANT INV to 6NT