BulletML, in short, is a XML-based way of controlling bullet patterns in shooting games. Read the full introduction and get the plugin in this thread
Since it's a tech-ish demo, BML was used for more than just enemy firing patterns: enemy movements and player fire modes also use the same system.
Download the demo (contains exe and .cap) (11 MB)

I must say that making even this bite-sized snack game took unbelievably long

Feel free to re-use any parts of this demo.