2D sprites, layers, movable object.

Hi, I'm still a beginner in Unity and 3 weeks ago I started to create a 2D shooter video game. the goal is basic, there are waves, and you have to shoot down the bots. I added for fun, a "splash" each time a bullet hit something, like a wall. Everything was working fine until I started to add movable objects (Such as wheel) As you can see in the video linked below, I managed to make it so when you shoot directly at the wheel, the splash follows the wheel rotation (which is cool) but the problem is I don't know how to set up the layers to make my big cube hiding the splash (In the video the splash on the wheel goes over the wall). And then, i have another problem, as you can see, when my little turret exploded near the wheel, its splash (which is INDIRECTLY splattered onto the wheel) won't follow it around (which is logic) but I would like it to do so! If you can help me, even just with keywords I would be thankful. And if you can give me as much details as you can then...I would put your nickname in the credits (Maybe one day it'll a AAA game who knows)

https://youtu.be/Qtr9K22nzgA

Thanks again :)))