COBRA is quite similar to the Schenken system, as described in Schenken's _Better Bidding in 15 Minutes_; even some of the specific criteria are similar or identical. The COBRA system was optimized by computer. Additional conventions were not introduced if they made a difference of less than .01 IMPs per board. I don't know whether the author of COBRA automatically started with the Schenken system as his basic framework before optimizing the system; it looks as though he may have, since several bids have exactly the same limits, and the responses to 2D, although apparently non-optimal, are essentially identical to those in Schenken's book. The book includes a system summary; I have used this as an outline but added more details so that I can describe the system rather than giving an outline for players playing against it. The book is available from IPBM 455 Alfreton Road Nottingham NG7 5LX England Phone: +44 1159 422615. Hand evaluation: COBRA evaluates hands both by HCP and PP (playing points). The PP evaluation system is dynamic; its function is to give numerical values to strong suits, well-placed honors, misfits, etc. Humans can talk about "good 14 counts"; while a computer cannot do this, it can say that a particular 14 count is now worth 15, and bid accordingly. The system is designed so that a partnership with 28 PP can expect to make ten tricks more than half the time; each additional trick requires another three PP. This is higher than in standard hand evaluation methods; the reasons are that values increase significantly when a fit is found, and that long suits have much greater PP value in COBRA than in conventional methods. The value of a long suit is one point for a biddable suit (Axxx, KJxx, QJTx, xxxxx), plus one for the next card, plus two for the next card, plus three for evey card beyond that. The basic PP also makes adjustments for aces, tens, and unprotected honors. General bidding principles: In constructive auctions, a limiting bid is made whenever possible, with a few exceptions. Limiting bids are raises, rebids of suits, and natural NT bids, including jumps; they are not limiting when made in forcing auctions unless they cancel the force. Competitive bidding is based on the law of total tricks. On a competitive auction, COBRA will contract for as many tricks as the partnership holds in trumps, and then double the opponents if the strength is evenly divided and the opponents are above their total number of tricks. Many competitive overcalls require a minimum difference between the length of the suit bid and the number of cards in the opponents' suit; this allows overcaller's partner to calculate the number of total tricks. Constructive bidding: All opening bids (even preempts, but preemptive hands usually reach these totals because of the points for long suits) require at least 13 PP, except in third seat. 1C opening: 18+ PP, 14+ HCP, forcing. Not made on hands suitable for 1NT, 2D, or 2NT openings. A positive response requires two aces, or 9 HCP with 1 1/2 honor tricks, or 10+ HCP; it is forcing to 3NT. Negative responder bids 1D; opener jumps in response to 1D with 23+ PP. Over 1-level or 2-level interference, most positive hands double. Over 3-level interference, negative doubles are used, but no other conventions. 1D/1H/1S opening: Natural. Spades must be biddable, hearts at least Qxxx, diamonds at least xxx. 1NT response to a major is forcing; opener's 2D or 2H rebid shows a biddable suit, 2C is artificial. Limit raises. Weak-suit game tries in minors (partner assumes three losers). Penalty doubles over non-jump 2-level overcalls; negative doubles over 1-level overcalls and single jump overcalls. 1NT: 15-17 HCP; third seat psyches 1NT 50% of the time if vulnerability is favorable with 18+ PP when the opening would have normally been 1D. 2C is Stayman, 2D and 2H Jacoby, 2S minor-suit Stayman, no Texas transfers. All 3-bids game-forcing; transfer to hearts followed by a 2S bid to sign off in a minor. 2C opening: Natural, rebiddable clubs; may be a preemptive club hand which does not qualify for 3NT or 4C bids. 2D is an artificial inquiry. Penalty doubles over 2-level intervention; negative doubles over 3-level intervention. 2D opening: Artificial, either a balanced hand with 23+ HCP or a one-suited hand with 8 1/2 playing tricks. Responder shows aces, and may be asked for kings and queens as well. 2H/2S openings: Weak, 6-card or good 5-card suit. 2NT is the only forcing response. 2NT opening: Two-suited hand with singleton or void in spades, 16- HCP, 18-22 PP. Artificial responses of 3C/3D/4C with 0-3/4-7/8+ HCP; other suit responses show long suits. No special conventions over an overcall. 3C opening: Solid 6-card club suit, hand too weak for 1C and inappropriate for 3NT or 4C. 3D response is Stayman; other responses natural. 3D through 4S: Natural, preemptive, playing strength within 2/2.5/3/3.5 tricks of bid depending on vulnerability (subtract 1/2 trick if the hand has at least a doubleton in all suits higher than the long suit). Preempts above the 4-level are not used. 3NT opening: Gambling, solid minor suit. Slam-bidding conventions: Gerber with Roman responses (4S shows two aces of same color or rank, 4NT two of same shape), 5-ace Blackwood. Defensive bidding: Over natural 1-bids or natural 2C: Cue-bid similar to a takeout double, but shows a void in the adverse suit; takeout double promises at least one card in the suit. Responsive doubles through 3S. 1NT shows 18-20 over 1C, 17-19 over 1D, 16-18 over 1H/1S. 2NT over 1-bid unusual, may be any two-suiter over 1S, otherwise two lower unbid suits; 2NT over 2C undefined. Weak jump overcalls. Over strong artificial 1C or 2C: Double with strong hands, including any hand with at least the strength shown by the artifical bid, or 14+ HCP and no suit good enough to bid at the appropriate level. Jump overcalls are preemptive; simple overcalls need not be. Over weak 1NT (minimum less than 15 HCP): Penalty double denies singleton or void; any other bid requires one. 2C shows any major-minor two-suiter, 2D shows both majors. Over strong 1NT (minimum 15+): Penalty double denies singleton or void; any other bid requires one. All overcalls natural and preemptive. Over preempts: Doubles are optional over 3-bids, penalty over 4H or higher (but double of 4H guarantees four spades), takeout over 4C/4D.