Obtaining interaction and engagement in large group teaching can be challenging, in particular in STEM subjects where it is essential to be able to efficiently present symbols, equations and formulae. Pingo is a free, web-based system that provides an excellent way of introducing interaction in large group teaching, as there are no restrictions on the number of participants. It is particularly useful in Mathematics-based subjects as it is TeX compatible. Such interaction also provides feedback to students and lecturers and it is a straightforward, but creative way to enhance student engagement. The author has tried and tested Pingo weekly in Mathematics and Statistics modules. This article provides all the information and resources required to start using Pingo along with some reflections on its use in the Mathematics Department at Swansea University.