Although this is a self-developed project, the game would not be made possible with the help of other talented developers offering materials, textures, and music in the Unity Asset Store (in addition to some of the packages that already exist in Unity).
Some of the developers that have mainly been used in the game is Aquarius Max and Yughes, offering furturistic/sci-fi materials, and Grumble Labs, offering background music to the game.
When playing the game, be sure to check out these great developers and their work.