The purpose of this mod is to speed up development of blueprints, particularly
for rail junctions.

Usage

Craft a "Symmetry Center" item. Place it in the world as a "Symmetry Center"
entity. Place some entities nearby and see them duplicated around the center.
Remove those entities and the duplicates will be removed.

Configuration

The Symmetry Center entity is a constant combinator. Setting signals within it
will control its behavior as follows:

• C
  Move the center of symmetry to a corner/edge of the tile. 0 = north edge, 1 =
  northeast corner, ..., 6 = west edge, 7 = northwest corner.
• D
  Set the max distance from the center to copy entities. Default is 64. Negative
  numbers are circular distance, positive square.
• R
  Rail entities are always placed on a 2x2 grid. This setting controls whether
  other entities honor that grid. -1 is never. 1 is always. 0 is not until a
  rail entity is placed then it automatically becomes 1. When this is enabled,
  the C signal center calculation is based on the rail grid (as if the center entity
  is 2x2 instead of 1x1).
• S
  Type of Symmetry. 0 = None. Positive = rotation, 4 and 2 are useful, other
  numbers are just pretty. Negative = mirror, -1 = east/west, -2 = north/south,
  -3 = both.
• item
  Positive signal will copy only the signaled item(s). Negative signal will
  exclude the signaled item(s) from copying.

Bug reports on the mod portal may not be seen. Github issues are preferred.