I like the concept. The art and the music work really well. I'm not super sold on having to go to the end door to get the code, though. I'm not sure if it changes on later levels, but I found it a little tedious having to walk the same path multiple times. It was be super great to have it as a side objective, like a terminal that you have to get to or a letter you have to find.
Either way, cool game!