So, now it's time to build the game! That is, to compile and package the game into a standalone and self-executing form, which the gamer can run and play without needing to use the Unity Editor. Typically, when developing games, you'll reach a decision about your target platform (such as Windows, iOS, Android, and others) during the design phase and not at the end of development. It's often said that Unity is a 'develop once, deploy everywhere tool. This slogan can conjure up the unfortunate image that, after a game is made, it'll work just as effortlessly on every platform supported by Unity as it does on the desktop.
Unfortunately, things are not so simple; games that work well on desktop systems don't necessarily perform equally well on mobiles and vice versa. This is largely due to the great differences in target hardware and industry standards that hold between them. Due to these differences, I'll focus our attention here to the Windows and Mac desktop platforms, ignoring mobiles...