This is where you will transfer what you've conceptualized, designed, and prototyped into the actual game. Generally, this is where you begin integrating it into the game engine, working on the actual models that will feature in the game. At this point, you're no longer prototyping, but developing the game. From here on out, you should have a clear idea of what your game is and how it will work from beginning to end. Once you have begun implementing your assets into the actual game, you will go through various iterations. These iterations will often occur after playtesting, albeit informal or formally done (for example, open/closed alpha, beta testing). The projects in this book will start at this stage. This is because we already have assets ready for you to use. But it is important to know at what stage of the game development process that implementation is at.