EGG is a new toolkit that allows researchers and developers to quickly create game simulations in which two neural network agents devise their own discrete communication system in order to solve a task together. For example, in one of the implemented games, one agent sees a handwritten digit and has to invent a communication code to tell the other agent which number it represents. A lively area of machine learning (ML) research, language emergence would benefit from a more interdisciplinary approach. However, the barrier to entry is high, as modern discrete-communication games require expertise in advanced areas of ML, such as deep sequence-to-sequence modeling and reinforcement learning. EGG lowers this barrier and makes it possible for scientists, engineers, and hobbyists with basic programming skills to design and test new games.