Don’t take it personally; earlier in my career I passed a coding test that was part of a five step interview process by writing my own game engine, and got hired — yet the exact same thing happened to me with this test; they told me my code wasn’t production level enough and I used too many external non-Unity features for my extra stuff. While I respect their desire to make sure their engineers can write quality code, it’s a little unrealistic to expect production level games from interview candidates who aren’t getting paid. Oh well.