Somer Assault, known as Mesopotamia in Japan, is a video game originally released by Atlus in 1991 for the PC Engine (later in 1992 for the U.S. TurboGrafx-16 release). This side-scrolling puzzle-based action game features an unnamed pink slinky as the protagonist which can fire bullets from its sides, jump, and slink along walls. The title "Somer Assault" is a play on the word somersault, as the slinky somersaults around the stage assaulting enemies.
Source: Wikipedia, "Somer Assault", available under the CC-BY-SA License.