When you start a video game project, your ideas may look and feel functional, but to be sure, you need to test them: this way you can ensure the success of your video game.
The ideal is to start the prototyping phase at an early stage. The purpose of this is to discover as early as possible various interface or mechanical problems that can be easily solved.
Game prototyping should be used as both idea generators and alternative exploration solutions. Because game prototypes are physical representations of your ideas, it allows you to think by doing, which means you will gain more value from the research, definition, ideation and testing processes.
You need game prototypes because they will help you explore and experiment with ideas, problems and opportunities and test the impact of the changes you will make during the project.