UPDATE 1 MAR 2020:
Fixed an issue where the enemy ships were occasionally spawning off-screen.
One of the things I've learned so far in this gamedev journey: Don't expect major progress on a daily basis (especially if you're just a one-man show that's also working a normal job). Days might pass where the game doesn't really change a whole lot. But the key thing is to just keep grinding away at it and try and make some sort of daily improvement.
At this point I could rush ahead and start coding other things -- more enemy ships, more weapons -- but that doesn't really make sense when there are still other game-breaking issues that need attention.