Slymoids

You're a cowboy fighting off the Slymoids with your gun. They're coming in from the horizon and from the sky. When coming in from they sky they move about from side to side as they slowly descend to the bottom of the play field. You can shoot up in the air at the flying Slymoids, or left and right at the ground dwelling Slymoids once they've reached the front of the screen where you walk to the left or right on the ground.