Each (non-trivial) sentence is initially reduced to a sequence of words that is easy to understand (e.g. subject, object, verb). In this initial version you will find at least one bracketed sequence of dots. Click these dots to unfold the sentence into a more complete version, in which the brackets are replaced by (underlined) extensions. By repeating this unfolding process you generate the complete version of the sentence step by step (gradatim). When eventually the complete version of the sentence has been presented, you will get to the next sentence by clicking Weiter.
The new page then displays - separated by a horizontal line - the sentence that you just worked on together with the initial version of the next sentence. Thereby, the immediate context of the previous sentence is always available for reference.