Gemini Wing is a gorgeous shooter for the X68000. Vivid colors with tons of small and medium sprites, plus a huge one for boss fights. It supports MIDI if you have the setup. Some enemies drop powerups but rather than simply adding them to ship, they follow you around in the form of single-use tokens. The tokens are processed FIFO (first-in, first-out, a term I learned in my 7am accounting class 30 years ago, and about the only thing I remember from it), so the one closest to your ship is used when you activate it.

I think I recall being able to clear level 1 and progress somewhat in level 2 without too much difficulty a couple of years ago, but when I put it in my X68000 last night, I found it pretty hard. There is an enemy that travels stright down but once it reaches your latitude, it moves directly at you. They usually travel in fours, so once you are spotted by one, you have to get out of the way, which usually puts you in a tighter space for the other three. I'm sure I just suck.