Keep in mind when making a hitbox you will probably have to handle SOCD (simultaneous opposing cardinal directions), many games don't handle up+down or left+right in a sensible way, the exception to this being if you're using a Cthulhu PCB and not any other PCB with your hitbox, as the Cthulhu has a built-in filter.
This is only tangentially-related, but I always wanted to make a Saturn/Dreamcast/PS2-compatible homebrew twinstick setup for Virtual On. Has anyone figured out a logic diagram (with 7400s or something, although a microcontroller may be simpler in this case...) where you have two sticks, two trigger buttons (weapons) and two thumb buttons (dash)
+ weapon "C"
or + or or or dash
I can probably figure it out on my own, but I hate duplication of labor. I just want to know if anyone has done it.