Double Dragon Neon Movement

Hey all, I
m trying to implement a 2.5D style beat em up but I can’t get my player or the NPCs to move up down left right while keeping the rotation at either 90 or -90. If you’ve seen Double Dragon Neon, they move up and down while keeping the rotation facing left or right. Any help would be great.

Twin Stick Shooter for example controls movement and player direction separately. Perhaps that as a base but lock down the rotation even more.

Thanks King Scott, that got me thinking in the right direction. I was thinking to deep into it. I just need to get the look at rotation to my player and if its greater than 0, rotate to 90 degrees or if its less than 0, rotate to -90