Arno is very similar to Roman, but retains a feature of Vienna that Roman has discarded: a strong artificial 1NT opening. In the case of Arno, it is game-forcing. The 1C opening therefore does not include the game-forcing hand, and instead includes a 17-20-point club 1-suiter.The club hand is shown with the cheapest club rebid, and the club canape' (which Roman shows with the cheapest club rebid) is shown with a jump rebid (which in Roman shows a game-forcing hand).The 17-20 HCP balanced hand is opened 1D, a bid that is perhaps a bit underused in Roman. (When opening in a 3-card fragment the lower one is selected, but otherwise there is nothing in Roman to make a 1D opening more frequent than 1H or 1S.) Arno also guarantees 4 cards in a major suit opened, so 1D may sometimes be bid with club 1-suiter and very short diamonds. After a 1D opening and cheapest NT rebid (17-20balanced), Gladiator is used. Over the 1NT opening, responder shows number of aces by steps [Not one of my favorite features of this system].Otherwise, which is to say most of the time, Arno is essentially the same as Roman.