The problem set 0 of Harvard’s CS50x 2020 edition was to create a small application using MIT’s graphical programming interface Scratch. I decided to make this tiny (tiny!) game.
For many years, long before the trend of retro games, I thought someone needed to make a Defender clone set in a pixelated sky above the pixelated cities of the world. But no one did and I myself never got further than a few scribbles.
Fast forward to 2020, when I embarked on my journey to get back into software development after a long hiatus. I started with Harvard’s excellent CS50x while figuring out the way forward. The problem set of week 0 was to create a small program in Scratch under these requirements:
- Your project must have at least two sprites, at least one of which must resemble something other than a cat.
- Your project must have at least three scripts total (i.e., not necessarily three per sprite).
- Your project must use at least one condition, one loop, and one variable.
- Your project must use at least one sound.
- Your project should be more complex than most of those demonstrated in lecture.
I knew immediately what to do: build a very simple version of that Defender clone I had in mind way back when. And that’s exactly what I did and you can play it here to save Berlin (where I am based) from over-tourism. Clearly this is a pre-Covid-19 scenario when tourism was still a thing.
Scratch code
Player sprite
The player sprite, a very basic rendition of Berlin’s iconic Brandenburg gate, can’t do much but move around an disappear when hit.
Bullet sprite
The bullet sprite handles the shooting. A hidden prototype is parented to the position of the player. Upon firing a clone is revealed and set in motion, only to be deleted when hitting an enemy or the screen edge.
Enemy sprite
The enemy sprite is the most interesting. A hidden prototype clones itself in ever shorter intervals. The clones on the other hand become faster as the game progresses. They disappear upon contact with the bullet and trigger a “game over” when they touch the opposite edge of the screen.
