Need help - 3D SideScroller ground shader

Hello,
I am currently making a game that is a 3D SideScroller and i have been struggling on making a material that makes the ground , walls and ceiling look like they are black or not recieving light on one side , like for example in the game Grime or Metroid Dread.
Since i haven’t been able to find any tuts or resource on this i was wondering if this effect has a name and if anyone has any tips on how to make this .

So far this is what i have made and i am wondering how to add a gradient to this or if this is even the right approach for what i want to make.

I am a beginner when it comes to this stuff, any tips or direction on any specific topic to research to make this better is welcome.

Thank you.