"Salamander (沙羅曼蛇), retitled Life Force in North America and in the Japanese arcade re-release, is a scrolling shooter arcade game by Konami. Released in 1986 as a spin-off to Gradius, Salamander introduced a simplified power-up system, two-player cooperative gameplay and both horizontally and vertically scrolling stages. Some of these would later become the norm for future Gradius games." Source: Wikipedia, "Salamander_(video_game)," available under the CC-BY-SA License.