It has a background that is static and the Diarama in front which is figures that are normally on a plate or pulley system that loops... you fire at the targets and a coil pulls in and the target then falls backwards so you cant see it anymore. All EM gun games have this to a certain extent.
My MONSTER GUN has a dual plate Diarama,
Viewed like this as a game


And this is the Diarama... 2 spinning discs that turn in opposite ways. The round monster targets when hit fall backwards taking them out of target.. illusion is that they disappear