Made for teaching Scratch at the Onna-son Children School of Science in Okinawa, Japan. The teaching plan is to let kids reproduce the code in this project, then show them a bunch of modifications (score, sounds, win animations, weapons...) they could do without giving them the code and then let them add the features they like. Has been tested in a 2-hour introduction to Scratch to middle-schooler and found very effective.
An example of possible features to add here: https://scratch.mit.edu/projects/118724232/
