style, naming, and arg-parsing changes
style changes and flake8 fixes
style, comment, naming fixes
move display function into display module
more refactoring
adds explicit namespacing to main
changes confusing function name
adds basic testing, refactors some thangs
almost there with rendering an invader...
a spinning alien!
renders basic alien field
creates world, moves alien field across it
factors out draw alien field and inits barriers
adds barrier source
moving player, sensible model-view relationship