So the basic idea of this is a physics based inventory, which honestly sounds like a nightmare but it would work well as the primary mechanic in a survival or rpg. Think of interacting with objects in your 3D environment, and when you want to store them in your inventory it pulls up a 2d representation of your inventory, and the object can only rotate relative to the angle you picked it up at. When you drag it back out, it’s 3D again.
Would be a neat challenge trying to keep your inventory nice and clean but also making room for objects based on size and even using perspective so that objects take up less space. For example, you might have a longsword but not much space, but if you’re looking at the longsword from the right angle, it has a much smaller profile, and hence will take up much less space when it gets squashed into 2D.
Here’s an imperfect example with a shotgun:
It’s interesting because you can go the extra mile and carry as much as you want, but it makes it harder to identify individual objects and you’re going to waste a lot of time if you accidentally spill the contents of your inventory. There may also be things that affect your inventory, like if you’re in a battle the contents might be shaken around, or if you’re drunk or there’s an earthquake or running or something.