Make number of notes always the same.
I would like my students to be able to differentiate between skips and steps without any hints from the illustrations. For example: Let's say one stick person has three skips going up in the diagram and another stick person has an incline. If the student hears more than three tones going up, he/she is more likely to click on the incline because the skips show three levels. The student would base his/her decision on sight rather than hearing.