Cappelletti Over NT

Over An Opening 1N Bid:

Dbl shows any 16+ HCPs
2 shows a one-suited hand
2 shows both majors
2 shows Hearts and a minor
2 shows Spades and a minor
2N shows both minors 
An exception to the above is that with a strong two-suiter which includes a major, you can bid 2N (supposedly showing minors) and after partner picks a minor, bid the major.

Responses To 2C:

Pass shows a good 6+ card Club suit.
2N shows 11+ HCP and a balanced hand.

- the Cappelletti bidder can then bid game with a maximum.
2 is an artificial bid to allow partner to bid his suit. The Cappelletti bidder will then rebid:
Pass if his suit is Diamonds
2 if his suit is Hearts
2 if his suit is Spades
3 if his suit is Clubs
2N with 4 Diamonds and 6 Clubs

Responses to 2D (Majors):

Pass shows a good 6+ card Diamond suit.
3 shows a good 6+ card Club suit.
3 is a preempt with 4+ in the suit.
2N shows 5-5 or more in the minors except that if the Cappelletti bidder then picks a minor and responder then bids a major, responder is showing a game invitational hand. 
2 shows responder's better major, which could be short since without one of the hands above, responder is forced to choose a major.

Responses to 2H or 2S:

2N denies support for the major; asks for the minor
- except that if responder raises the major over the minor suit rebid by the Cappelletti bidder, he invites game in the major (normally, 11-12 HCPs). 
Pass shows support for the major and <8 HCPs. 
Jump-raise to 3 level shows a fit and 8-10 HCPs.

Other:

In Pass-Out position, Dbl shows a four-card major and a longer minor.

Cappelletti can also be used over 2N or 3N opening bids.

It can also be used after a 1N overcall of partner's opening bid of 1 or 1, where it shows <8 HCPs, since with 8+ HCPs, a penalty double should be made instead.