Ah, this is very helpful. Thanks for clarifying.
First of all, students do not design games like NinjaCat. They are similar, but don't include things like jumping or gravity. Getting the sourcecode to NinjaCat would be about as helpful as getting the sourcecode to TombRaider in this context. :)
Finally, however, I'd caution you against answering questions by referring to code. Most of the time student errors happen on paper, as they're thinking through the Design Recipe. If a student runs into trouble and has a question, debugging code is often the worst way to help them sort it out: the bug is in their thinking, not their code! This is why we use a student workbook, and why we provide an answer key to this workbook. I recommend starting there.