Homeworlds Game Record Notation

I recommend a slight variation of the notation used on Abstract Play (aka AP or SDG 2.0).

Actions

• homeworld <star1> <star2> <ship> <systemName>
• build <ship> <systemName>
• trade <ship> <systemName> <newColor>
• discover <ship> <oldSystemName> <newStar> <newSystemName>
• move <ship> <oldSystemName> <newSystemName>
• attack <ship> <systemName>
• sacrifice <ship> <systemName>
• catastrophe <systemName> <color>
• pass

Notes

A color is denoted by the lowercase first letter of its name in English, such as "y" for yellow.

A piece (i.e., a ship or star) is denoted by its color's letter and its number of pips, such as "g2" for a medium green.

Multiple turn actions are simply concatenated in the order they are performed, with any convenient character separating the actions, for example
sacrifice y1 Alpha / move b1 Beta Gamma / catastrophe Gamma b
AP separates actions with commas, SDG used line breaks.
I like line breaks when possible, but when commands need to be on one line, I favor semicolons ; or slashes /.

Optionally, you may write "pass" in place of an unused sacrifice action, as in
sacrifice r3 Alpha / attack b1 Beta / pass / pass

Actions can also be abbreviated by first letter: "h" for homeworld, "a" for attack, "c" for catastrophe, etc.

A new system is given a name when the system is discovered. The name can be any string that doesn't interfere with notation.

• The name must be different from the names of other existing systems.
• For clarity, the name should not resemble other recording notation. For example, "catastrophe" is a misleading system name.
• Many players use piece notations of stars as system names, such as naming a system "g1" if it has a small green star.
  If you like such system names, I recommend avoiding confusion by using uppercase letters for system names. For example, use "G1" for a system name and "g1" for small green pieces.

When establishing a homeworld, AP does not denote a name for the system. I recommend doing so in order to make the record complete.

When building, AP actually only lists the color (not size) of the built ship, as in build <color> <system>. I suggest including the size because it helps to readers who replay the game by making bank state errors more obvious.

When trading, AP's notation subtly different from the SDG notation trade <ship> <newShip> <system>. The choice on AP to record the color (instead of the ship) avoids confusion when systems share names with pieces.
For example, SDG's annotation trade r1 b1 g1 (meaning "trade r1 for b1 in the system named 'g1'") looks like it might mean "trade r1 for g1 in the system named 'b1'."
AP's annotation trade r1 g1 b is more clear unless there is a system named "b."

Looney Labs is trying to phase out the term "attack" because it suggests destruction rather than a change of ownership. Their preferred term is, "capture." However, I still prefer "attack" for notation because it does not share a first letter with other actions. "Capture" would be abbreviated "c," which may be confused with "catastrophe."