PC or MAC computers/laptops needed. Download not available on mobile devices. To make your own game, download the software and learn.
To make a video game, you need a game design software. Thousands of game assets called "UNITYPACKAGES" let the software build a game. DontGiveA.Com Productions has an extensive library.
If you use YOUTUBE, you can find thousands of videos on how to do specific things in your game projects. Whatever your imagination can come up with, there IS a way that you can design it in 3D space and interact with it.
Just like any other software, there is a professional version available for sale. Using the FREE game engine still allows you to design games. To make games more realistic, you will need the pro versions. Learn the ART and come back and help!