This is the third lesson in the ‘App Inventor’ scheme of work. This lesson introduces programming concepts including; Variables, data structures & the randomise method in a completely interactive manner. All lessons within the scheme are targetted at KS3/KS4 and appropriately mapped to elements of the Computer Science 9-1 GCSE. Each slide includes detailed notes to support teacher understanding and have been based on a lesson plan structure. There is no prior knowledge required from the class teacher as the guides provided are step-by-step & all code is catered for in the documentation provided. Using the ‘App Inventor’ emulator or a mobile device with the 'MIT App Inventor app’ installed will allow learners to practically use the apps they build. The app can be downloaded freely from the ‘Google Play’ store.