Response Over Opp's takeout double - folksbridge21/system2 GitHub Wiki
低花开叫后：
1C-(X)-XX - 10+
1C-(X)-1x - suit at one level forcing one round
1C-(X)-1NT: 8-bad 11p
1C-(X)-2C, 简单加叫，6-10
1C-(X)-2NT : 约旦2nt, 10-11p+
高花开叫后：
1H/S-(X)-2H/2S: 3 card support, <=8 pts
1H/S-(X)-3D/3H: 4 card support, 8-10 pts
1H/S-(x)-1NT: 3 card support, 8-10 pts
1H/S-(X)-2NT: 3-4 card support, 11-12 pts (约旦2nt)
1H/S-(X)-XX: indicate no major support, 9+ pts
1H/S-(X)-2C/2D: natural, non-forcing, <10 pts
xyz is on, drury is off, bergen is off, inverted minor is off