In the lesson 'Pour que (so that, in order that) is always followed by Le Subjonctif ' it states that the subjunctive is used: When something happens so that / in order that someone else does something.
The translation given for 'so that shapes appear' is 'pour que des formes apparaissent'.
As there is no 'someone else' involved here, presumably apparaissent is not in the subjunctive?