I first stumbled upon this game in the 1990s in my school’s computer laboratory. I wanted to develop something similar on my own but the little GW-BASIC programming I knew and the very limited access to computers (<= 3 hours per month) I had wasn’t sufficient to take on an endeavour like this. I did write a few simple text adventure games and a BRICKS clone too. But writing an invaders-like game was too challenging for me back then.
Finally, three years ago, I sat down one afternoon and fulfilled that childhood dream of mine.
Here’s the result: https://susam.net/invaders.html
It’s a single HTML page with no external dependencies, so you are very welcome to “View Source”.