I'm thinking about making my own simple game engine and a level editor for my next game and I was wondering, how does a "build" button works for example in Unity game engine window? How are these used assets, scripts, models, textures packed? How are these being playable? Can someone explain what happens behind? P.S. I'm not sure if techniques are the same or different on each platform, but I'm looking for techniques for an android platform. And I'm not concerned to Unity only, would love to know different techniques.