The "world.rkt" module now uses a non-S-expression syntax, as enabled through the change of the first line to #lang reader "txtadv-reader.rkt" The new "txtadv-reader.rkt" module parses the syntax of "world.rkt" and generates the original form as a syntax object. The "txtadv.rkt" module language is unchanged, since "txtadv-reader.rkt" converts "world.rkt" to its old form.