This feels like a good start on a fun little pinball game!
Audio could definitely add a lot to what's already here. Scores not resetting after losing a ball/not having a limited number of balls also feels like a small fix that could enhance the experience.
The space invaders are a nice touch, and I like the way the wall bumpers affect what would otherwise be a less interesting surface to wait for the ball to roll down.
In your instructions for setting executable permissions, you should probably note that the relevant setting will be in the properties dialogue of the the user's file browser specifically.