This was pretty cool - and bonus points for making this on a literal GameBoy. Took me a little while to figure out what was going on and why I kept dying until I read the description like an intelligent human being. A very clever concept, very tricky!
I found I basically wound up mashing B and A at all times. It's not necessarily bad, but it means there wasn't really an interesting decision there - I always want to be shooting and switching between ghosts, the interesting decision is where do I want to be and which direction do I want to be facing? I think some of the ideas discussed below where you can't switch or shoot as often would be good, but there would probably have to be fewer ghosts (maybe 5 to 9, in keeping with the apocryphal rule of thumb about working memory).