Thinking of merging holy diver/Castlevania with Double Dragon beat them up elements somehow. And wall climbing.

Probably put easy and hard mode in. Easy mode just less foes and less damage from foes. Hard mode linear but more tougher foes and more damage. Hard mode male character, easy female.
I could make run n gun or beat em up or platformer.

Unreal is easy to use. Probably will use that. But old 8 bit style music.