In college I played Nethack. Then I moved to Moria. Now I stick to playing Angband.
I read an article about the Unity game engine/framework. Thought I better jot down some notes so I can remember what I read. You design games with Unity. It supports two or three dimensional games. However it does not provide asset creation functionality. For that you need Photoshop or 3D Studio Max or Maya. As you may know, those programs cost $$$.
Now for some Unity terminology. Packages contain resources. Your game is broken down into levels called scenes. You add GameObjects to your scenes. And you add Components to your GameObjects. Make sure you use Unity to modify your game. Don't hack the files you find in the folder created by Unity.
Click the Play button in the Game tab to run your game. Beware that while the game is running, you are in a special mode, and changes to your game are not saved. That feels like a bug.