Gaming

Do you want to? Go for it.

Does your game crawl? Have you identified this code as the bottleneck? Are you certain that asm will give you a meaningful performance increase, and that your issue doesn't lie with your approach to the problem? Sure, I guess. You said your game runs fine though, so this probably doesn't apply.

Is your game fast already? If you don't want to do it, don't.

Writing asm by hand is almost always a waste of time. There are only a few times where it's actually necessary, and unless you're writing a bootloader and running your game on bare metal, I can't imagine why it'd be necessary. But you know your code better than anyone else here, so you should know whether it's needed or not more than any of us do.

To begin with, you're apparently targeting the Z80, which I haven't seen used for games in the wild... probably in my entire life? Maybe an arcade machine I played on once used it, but I can't think of any other times. If your targets need custom assembly, then you should already know that. We don't know your targets.