Add pgzero launch

[christo]

This fixes issue #1 and allows the game to be run using the conventional python invocation: python marble.py cc @bakerbrown

[orsenthil]

Thanks! I was wondering why the game was not working.

Why would the author not add this?

[christo]

I think it's when you use "pgzero" which is an easier to use pygame framework, a pattern of practice seems to be to use the pgzrun command that comes with it instead of using python and in that case the imports are unnecessary. See an example of this in the pgzero quick start docs.

https://pygame-zero.readthedocs.io/en/stable/introduction.html

It's actually a cool looking system - at least for beginners - and if there had been some direction on the listing about how to launch it from the command line I would probably not have made this pull request. This may also be why they haven't merged it yet.

Anyway @Wireframe-Magazine should say something - either say it requires pgzero to launch and link to the instructions for that or merge this pull request and add the imports. Adding the imports won't break the pgzrun method and it's not too much yucky noise for newbs is it?

[christo]

My conclusion is that Wireframe-Magazine is not interested in maintaining this.