I'm a reasonably experienced programmer and I've identified some areas in which I feel you could improve your program. Firstly, I'd like to congratulate you on building a working version of your game. I remember working on a similar project about five years ago and it was the first non-trivial program I completed in Python. It was then that I first felt the satisfaction of creating something meaningful with a keyboard and a text editor. Enjoy that feeling - it makes up for the frustration of fighting errors after crashes after bugs.
The first suggestion I would make to you would be to reduce your use of global variables. Beginner programmers tend to overuse global variables, as they are very simple to use. If all the information about your program (commonly called 'state') is stored in global variables, you don't have to think very hard about where it is stored when you need to use it. This might seem like a good thing, but when your programs start to get more complex global variables will qu