int first_level; // first level number (to allow start with 0 or 1)
int last_level; // last level number (automatically calculated)
int sort_priority; // sort levels by 'sort_priority' and then by name
int first_level; // first level number (to allow start with 0 or 1)
int last_level; // last level number (automatically calculated)
int sort_priority; // sort levels by 'sort_priority' and then by name