int levels; /* number of levels in level series */
int first_level; /* first level number (to allow start with 0 or 1) */
int last_level; /* last level number (automatically calculated) */
int levels; /* number of levels in level series */
int first_level; /* first level number (to allow start with 0 or 1) */
int last_level; /* last level number (automatically calculated) */