Keen's Two Bids
A full system of 2 bids -eeither weak nor strong
Essentially all 2 bids show either a Strong Two in that suit (20+ HCP), or weak two in suit above.
Two spades is spare and Tartan style. The 2-2 bids include strong balanced.
2C:A big hand or weak two in diamonds! (5+ card)
2D:Weak in hearts or Acol Two in diamonds or 19-20 2NT type
2H Weak in spades or Acol Two in Hearts or 221-22 2NT type
2S:Acol two in spades or 5/5 - Spades and another - Strong or 4-9
2NT:5/5 hearts and another 4-9 points
Response Generally 2NT game inquiry, next suit up to play. Opener continues with a strong opening.