Although it fits into the category of a non-natural system I feel it is a very simple system to play, and that actually relative beginners would be happy to play it and do reasonably well with it.
The general system is as follows:
1♣ opening promises a 4-card major, normal "opening bid" values (rule of 20 or even 21), a hand that doesn't qualify for an opening of 1NT or a stronger bid
A response of 1♥ or 1♠ promises a 5-card suit. This is one of the advantages - that the responder can show their 5 card major right away.
A response of 1♦ promise at least one 4-card major, asks partner to name, and the values for a response.
A response of 2♣ is artificial and this response is commonly used in the system to show game-invite values. In this case no 4-card major or you'd bid 1♦
A response of 2♦ is artificial, game force (but not necessarily interested in slam) and no 4-card major.
That leaves 1NT which is a general weak "to play" response, bids of 2 of a major (pre-emptive) and 3 of a minor (pre-emptive) and 2NT (both minors, pre-emptive).
1♦ opening denies a 4-card major. It could be bid though with 3-3-0-7 distribution.
The response pattern is the same. Of course here the 2NT response guarantees you'll find partner with at least one minor. 1NT could be bid with a 4-card major, there is no need to show it.
1♥ and 1♠ are 5-card major bids. 2]clubs] and 2♦ responses show game invite/forcing values and don't deny support.
The 1-level bids are all relatively limited. See the 2♣ opening. Although you can vary the system, of course.
1NT opening is usually 16-18 balanced
2♣ opening shows either:
- 18-22 unbalanced
- 19-20 balanced (will rebid 2NT)
- Weak 2 opening in diamonds
Responder will respond 2♦ unless he holds a hand that does not want partner to pass with a weak 2 in that suit. The system is not properly defined after that point other than the obvious opener bidding 2NT on the balanced hand and passing on the unbalanced one. Most of the time it comes up it is actually one of these two, the unbalanced 18-22 seems surprisingly rare.
2♦ opening is either:
- Game force
- weak 2 in either major.
Followed by 2NT is usually 23-24 with opening 2NT used for 21-22 balanced. Not determined what opener should do with a better balanced hand. I don't like 3NT as a response, as it cuts out Stayman and Transfers by responder's hand below game.
3-level opening bids are just pre-empts like in most systems.