Most papers on introducing children to computing assume the children will interact directly with the technology or task. In this paper, we reflect on a case of designing for indirect interaction - where it is not the children's hands but a facilitator's on the device. The context is a computing lecture we gave for twenty-six children aged between five and seven years old. This was specifically designed to give a stylized experience of being a university student - it is self-consciously a lecture emphasising student-teacher interaction around code. We found a technique from undergraduate engineering education - a partially exposed simulation in a text-based programming language - allowed imaginative interaction from the children as they discovered they could model the impossible.