You could try to make it 3d but let it look like a 2d UI, that’s possible,otherwise you would have to calculate the boundaries or use the function to get the color of a pixel to check if there’s a wall and if I you’d move there. If u can because there es no go slowly to the mouse pointer. If there’s a wall stop there.
You could set the player to be a red part. When you deactivate shadows and make the camera so you can view it from top and remove the texture you shouldn’t be able to see if it’s a GUI or not. If you want it to be a GUI you could use this.