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 object/creature 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 while assaulting enemies.
The story (existing in the export version only) is presented in a short prologue sequence at the game's start. "In a time and world not of our own", a wicked sorceress uses her evil powers in an attempt to conquer the world. She summons twelve powerful minions, each of them representing one Zodiac sign, and sends them to create havoc. Only the slinky stands in the way of her quest for domination and has to battle through 12 stages of enemies, destroying each Zodiac boss along the way, in order to reach the sorceress and put an end to her plot.
The slinky is able to move along the floor, walls, and the ceiling by slinking along them; it can also make a short jump to move between walls and platforms to slink to a different section of each stage. The slinky is also equipped with a machine gun that fires to both sides of it to take out the myriad of enemies that swarm you on each stage. The player is given several hit points which can be increased with power-ups as well as several lives should the player die and unlimited continues. A time limit is given for each level, and the goal is to reach the Zodiac boss of the stage and defeat it before time expires. On the final stage, the player must defeat all of the bosses in succession before being allowed to duel against the sorceress herself. When she's dead, a battle commences against the real end boss, "The Creator".
At the start of the game, the player is asked to enter his or her birthdate. This causes the player's Zodiac Boss to fire power-ups as gifts rather than damaging shots (for example, entering a birthday of April 27 will cause the Taurus boss to fire power-ups at the slinky rather than damaging shots).