Book excerpt: This book covers Android app design fundamentals in Android Studio using Java programming language. The author assumes you have no experience in app development. The book starts with the installation of the required development environment and setting up the emulators. Then, the simplest "Hello World" app is developed step by step. In the next chapter, basics of the Java programming language are given with practical examples. Screenshots and code snippets are clearly given in the book to guide the reader. After the Java lecture, 7 complete Android apps are developed again by step by step instructions. Each code line is explained. As the reader follows the development of the example apps, he/she will learn designing user interfaces, connecting interface objects to code, developing efficient Java code and testing the app on emulators and real devices. The last chapter explains the installation of the Unity game engine, developing a simple 2D platform game in Unity, setting up touch controls for Android environment and exporting the game as a standalone .apk file ready to be installed on Android devices. Sample apps developed in this book are as follows: 1. Headlight app: Learn the basics of app development and use buttons in your code. 2. Body mass index (BMI) calculator app: Using input boxes, performing calculations and displaying the results on the screen. 3. Simple dice roller app: Using random number generator functions, including images in your project, displaying images on the screen and changing the displayed image programmatically. 4. The compass app: Accessing the magnetic field sensor, setting required permissions, extracting the direction angle and animating a compass figure. 5. Show my location app: Creating a map project, setting required permissions, accessing GPS device and showing real time location on the map. 6. S.O.S. sender app: Adding SMS functionality, setting required permissions and sending real time location using SMS. 7. Development of a 2D platform game: Installing Unity game engine, developing the visual part of the game, implementing the game logic in the code, setting up touch controls and exporting the game as a standalone .apk file. This book includes 237 figures and 130 code snippets that are used to explain app development concepts clearly. Full resolution colour figures and complete project files can be downloaded from the book's companion website: www.yamaclis.com/android.