Clone Drone in the Danger Zone is made with Unity. There is a free version available for personal use, as well as licenses for commercial projects. It is a wonderful way to get into creating games, and helps you learn and develop your skills. If you ever get a chance, you can watch some of Erik's Twitch stream archives where he works in the Unity editor. It allows for feature additions and bug fixes in near real-time depending on the case. :-)
-Cheers