New game: Alien Intruder, a single screen jump-and-shoot arcade platformer for MS/DOS and compatible.
In space no one can hear you scream, so use your blaster instead!
Info and free downloads: https://www.usebox.net/jjm/alien-intruder/
@reidrac finally tried it. It's very cool and deceptively simple. I like that dying resets the score but doesn't put you back to stage 1: I don't really have all the time I had 30 years ago to play.
One thing I'd change: it's much more challenging to finish the game without killing enemies, so I'd invert the bonus and give points for every enemy left alive rather than killed.