Our 2C opener shows about 10–15 HCP with 6+ ♣. Good 9 HCPs with some extra shape are acceptable as well, especially in 3rd seat. Four-card or even five-card majors are possible as well. In 3rd seat, opening a good five-card club suit is allowed as well for lead direction/preemptive purposes.
2♦ Artificial asking bid, promising INV+ 2♥ / 2♠ NF constructive, usually about 7–11 HCP, 5+ card suit 2NT Puppet to 3C, showing either a weak raise in ♣ (most common) or a GF 5+ 5+ hand without ♣. 3♣ Constructive up to a mild invite, usually around 8–11 3♦ / 3♥ / 3♠ Nat, 6+ card suit, GF. 3NT To play. 4♣ Preemptive 4♦ RKC ♣ (Tom: CIRKLE?) 4♥ / 4♠ To play.
2♥ 4 cards in either major. 2S asks: ♥ min / ♠ min / ♥ max / ♠ max. 2♠ Maximum, no 4-card major, unbalanced or unsuitable for declaring NT. 2NT Maximum, interest in declaring NT. Bal or 6331 with stiff K. 3♣ Minimum, no 4-card major. 3♦ Maximum, 4+ ♦ Other Undefined.