Rubicon is a cue-sport drawing on the precision and tactics of snooker, the cue ball craft of billiards, and the combination shots of 9-ball pool. Its defining feature is the role of the baulk line — its Rubicon — which the cue ball must cross during a shot for any pot to score. Pots made without a crossing are respotted.
You can download the full, official rules of Rubicon here. For the casual reader, the essentials of Rubicon are these:
- Setup. All seven balls — the red and the six colours — are racked in a hexagonal cluster centred on the pink spot, as shown in the diagram below. The red is at the front; the black is at the centre; the pink is at the back; the yellow and green sit either side of the red; the brown and blue sit either side of the pink (brown behind yellow, blue behind green).
- The break. The breaker places the cue ball anywhere within the D and plays it into the rack, striking the red first. For the break to be legal, at least three balls (other than the cue ball) must reach the edge of the table — that is, contact a cushion or be potted. The break is otherwise an ordinary shot: pots score in the usual way (the cue ball must cross the Rubicon on its way to the rack), and continuation applies as on any other shot — a pot, cannon, or in-off keeps the breaker at the table. An illegal break is a foul.
- Object-ball sequence. Object balls must be struck in snooker order: red, yellow, green, brown, blue, pink, black. The cue ball must strike the next ball in the sequence — the designated object ball — before contacting any other ball.
- Scoring the object ball. A pot of the designated object ball scores only on a crossing shot — one in which the cue ball crosses the baulk line at some point before contacting the object ball. This is crossing the Rubicon.
- Scoring other balls. A pot of any other ball, after the cue ball has legally struck the designated object ball, scores regardless of whether the shot was a crossing shot. (The 9-ball-like feature of Rubicon.)
- Pot values. Red 1, yellow 2, green 3, brown 4, blue 5, pink 6, black 7. Multiple balls may score on a single shot; each pot is evaluated independently.
- Respotting. Pots that do not score are respotted. Each colour returns to its own snooker spot (the yellow, green, brown, blue, pink, and black on their standard snooker positions); the red returns to the red spot at the apex of the D. If a ball's own spot is occupied, it goes to the highest-value free spot. Pots made on declared safeties or on foul shots are always respotted, regardless of any crossing.
- Continuation. A pot, cannon, or in-off (without a declared safety) obliges the striker to take another shot. Cannons and in-offs do not themselves score, but extend the break — useful for setting up a crossing shot or improving the cue ball's position.
- Declared safety. A player may declare a safety before any shot. On a declared safety, the opponent comes to the table afterwards, regardless of what happens on the shot.
- Playing from the D. Whenever the cue ball is placed in the D following an in-off, the cue ball must, on that shot, contact a cushion above the baulk line (the top cushion, or the upper part of either side cushion) or a ball not in baulk, before striking any ball that is itself in baulk. The cue ball may be played in any direction.
- Fouls. A foul gives the opponent cue ball in hand, to be placed anywhere on the playing surface. Three consecutive fouls by the same player wipe that player's score for the frame to zero.
- End of frame. The frame ends when only the cue ball remains. The player with the higher score wins. If the scores are tied, the red is respotted and play continues until the red is potted on a crossing shot.
