idx

type Detail struct {
	FirstSprite uint16 // Relative offset from the group's SpriteIdx
	LastSprite  uint16 // Relative offset from the group's SpriteIdx
	Unknown1    uint16 // Could also be LastSprite? Something else? AtRestSprite?
	Unknown2    uint16 // Number of resting sprites, if we're AtRestSprite?

	Padding [12]byte // Set to zero in the cases I've looked at so far.

}

type Group struct {
	Spec    Spec
	Records []Record
	Details []Detail // Records and details are correlated by index
}

type Idx struct {
	Filename string
	Groups   []Group
}

type Record struct {
	// A guess, but each group of 8 records with increasing compass points share
	// this value.
	ActionID uint16

	Compass byte // It's odd to only have one byte. Maybe Unknown1 belongs to this too?

	Unknown1  byte   // ??? Only see values 0x33 and 0x00 for librarian.
	Offset    uint32 // Where the Detail for this Record is to be found.
	NumFrames uint32 // A guess, but seems to fit. Number of frames for this action + compass.
}

type Spec struct {
	Offset    uint32 // Where the Records for this Spec are to be found
	Count     uint32 // Number of Records for this Spec
	SpriteIdx uint32 // Index of the first sprite in
}