progress

type Progress struct {
	Version    int            `json:"version"`
	XP         int            `json:"xp"`
	Level      int            `json:"level"`
	Stars      map[string]int `json:"stars"`
	Completed  []string       `json:"completed"`
	Badges     []string       `json:"badges"`
	LastLesson string         `json:"lastLesson"`
	// Theme is the selected UI color theme (empty = default). It is a display
	// setting rather than progress, but it rides along in the same file. Added
	// after Version 2; omitempty keeps it out of older saves, and a missing
	// value unmarshals to "" so v2 files load without a version bump.
	Theme string `json:"theme,omitempty"`
}