Playing casual games is a wildly popular activity on smartphones. However, designing casual games is done by a smaller group of people, usually on desktop com-puters, using professional development tools. Our goal is to bring these activities closer together, in terms of who does them and how they do them. Our Gamika Technology platform is a 2D physics-based mobile game design environment. It comprises a 284- dimensional parametric design space, and poses mobile game design as the problem of navigating this space. We have built three mobile apps thus far to experiment with on-device, mixed-initiative navigation of the Gamika design space and some of its subspaces. We describe these apps here in terms of the initiatives that go into making a game with them, and how these are split between people and underlying AI software. Our overall goal is to democratise game design, so that an- yone and everyone can make casual games directly on their mobile phones or tablets.