[Home]Bifurcation

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It is possible for the game to bifurcate. When this happens, the game splits into two strands and players must move in both. In this situation, the game can only be won by playing Mornington Crescent in both strands simultaneously – or by recombining and then winning normally. Recombination occurs when more than twelve tokens (of any colour) are in the same quadrant and on the same line, and a player successfully brings both strands to the same station at the same time with complementary rather than opposing line velocities.

Example: Overall line velocity is +5 Northbound. One strand of a bifurcation has a line velocity of +3 NorthEast, and the other strand +4 NorthWest. In this highly simplistic example, a T 8.13° rotation (see spin) would combine the vectors and allow the bifurcation to be rejoined.

Bifurcation can be triggered in three ways: when the number of red tokens on the District line is at least three more than the number of blue ones on the Central line, if Beck's is multiplied by exactly 2.6, or optionally if the two stations are the same colour. Bifurcation is worth considering if you want to add confusion to the game or destroy an opponent's plans.

Tri-, quadri- and greater furcations have been known. As, indeed, have semifurcations – where only half a station name is played in one or more strands (a typical such move could be: Totteridge / Wealdstone). Even rarer are other fractional furcations. The record number of furcations known in any one game is 18, and the record number of strands open at the moment of victory is eight: both records were set in one game under the [Reykjavik '92]? ruleset – a variant ruleset which is not only notoriously lax about the conditions under which bifurcations and greater can occur, but is one of only two rulesets to allow both a nullifurcation (zero active strands) and a non-integer fractional furcation, where the station fractions do not add up to a whole number of stations.

(Not surprisingly, the Boardman's Combined Stations ruleset owes a lot to Reykjavik '92, on the rare occasions that Boardman's is actually taken seriously.)

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Last edited April 8, 2007 12:41 am by Simons Mith (diff)
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