This book considers the four essential cores of game design: Mechanics, the interactive elements that allow players to be part and interact with the game itself; Economy, the resources and numerical concepts that will enable players to evaluate and consider the options in the game, creating strategy, risk, and fun; Narrative, the textual features that enable players to create and generate meaning for the game and its parts; and the Aesthetics, the audiovisual elements that allow players to experience the game through their senses and feelings. This book discusses all four essential cores and how to design games by using each one as a starting point.It also discusses how each one is connected and can be understood as a valuable tool to elevate a game's design.It follows a practical approach to how we can implement the game design and development process by being prototype-focused, user-centred, and lean. This book will be of great interest to students, indie game developers, and aspiring early-career designers looking to hone their game design craft.