Every object you build, own, or attack is a typed entity with an ID of the form type-index (player 1-11, planet 3-4, and so on). This section is the catalog: what each struct type is, what it costs, what it does, and how ownership, power, and economy link those objects together.
Use struct types when you need stats, build costs, or weapon draws for a specific building. Use entity relationships when you need the graph — which objects sit on a planet, which player owns the fleet, which substation is feeding whom.
Generated catalogs in reference are stamped from a live structsd version and win when a number here disagrees with a binary you are actually running.
IDs are not cosmetic. The CLI parser treats a dash in 3-1 as a flag unless you put -- before positional arguments. Permissions attach to objects and addresses, not to “the planet” as a vibe. If you cannot name the entity type you are about to sign against, stop and look it up here first.
Open entities when an ID, a build menu, or a scout report names a thing you cannot picture. Struct types answer “what does this building do and cost.” Relationships answer “what else dies if this planet does.” Bring a structsd version. Numbers without a version are rumors. The generated struct-type catalog in reference is the page to trust when this prose and a binary disagree. If you are about to struct-build, you want the cost, the power draw, and the ambit of the weapon — all three, not a vibe. Guessing a type ID from memory is how you spend a build on the wrong struct.