Understanding RUL Flags
RUL files control the placement of network items in the game. An example of a network item is the road you drag out. RUL flags refer to a specific combination of hexadecimal values that tell each network tile what to do.
Network flags are the game’s encoding of transit network connections for a given tile. Each tile has four flags, one for each edge. A flag defines whether a connection exists across an edge and its relative direction.
Five primitive flags are used in the various RUL files:
- 0 - no connection
- 1 - left diagonal
- 2 - orthogonal
- 3 - right diagonal
- 4 - median (for double-width networks, e.g. avenue)
Individual Network RULs make use of additional flags:
- 11 - left diagonal to orthogonal blend
- 13 - right diagonal to orthogonal blend
Rail networks use additional complex flags:
- 21 - left diagonal switch
- 23 - right diagonal switch
- 22 - left secondary blend
- 42 - right secondary blend
- 32 - left orthogonal to diagonal crossover/switch
- 52 - right orthogonal to diagonal crossover/switch
- 62 - wye flag (also used for crossover/switch)
- 72 - ‘W’ flag (used for ‘W’ switches)
Individual Network RUL (INRUL)
Individual network RULs define the standalone behavior of the game’s twelve networks. Each network has a basic and advanced INRUL file. Basic INRUL defines typical placement, while advanced INRUL handles more complex situations.
INRULs are composed in a 5x5 grid of tiles in which flags and network piece IDs are defined. Conventionally, basic INRUL uses only tile to define a rule, while advanced INRUL defines multiple tiles.
Intersection Solutions RUL (RUL1)
RUL1 defines tiles for the intersections between two different network types.
Override RUL (RUL2)
RUL2 is used to override the results of INRUL and RUL1 definitions. It works by reassigning a pair of adjacent pieces to another pair, replacing one or both pieces. RUL2 is the mechanism used to create override networks such as SAM or RHW.
Intersection Ordering RUL (RUL0)
RUL0 defines interchanges, puzzle pieces and FLEX-style pieces which can be placed using menu buttons.