Z_Defense Against Multi 2D Opening - folksbridge21/system2 GitHub Wiki

Oppo 2D opening means weak two for one of the majors

https://www.bridgebum.com/defense_to_multi_2d_a.php

(2D)-X: 13-15 balanced
技术性加倍的牌等对手找到配合之后再加倍，所以直接位置加倍通常没有单张，e.g., 4441 13-15HCP 先不叫
(2D)-2H/2S/3C/3D: natural
(2D)-3H/3S:更好的牌，逼叫一轮
(2D)-4X: leaping Micheals
(2D)-2NT: 16-19
(2D)-3NT: to play, source of tricks

2D: 2 Majors
(2D)-X: 实力, 12+, 因为2D不可打
(2D)-2H/2S: 2H自然叫，2S扣叫双低花，黑桃套回头再叫
(2D)-2NT: 自然
(2D)-3H/3S: 询问挡张
(2D)-: 敌人叫过套之后加倍就是技术性的