Fun Fact: The Moai statues in Gradius, based on the real-life statues on Easter Island, would appear in many other Konami games in the future.
Gradius set the template for a host of follow-up side-scrolling shooters on the NES, many of which were also developed by Konami. Gradius was such an iconic game that the space ship players piloted had a name – the Vic Viper – which would appear in Gradius II and Life Force on the NES, and in numerous games on other platforms continuing to the present day.
Players controlled the Vic Viper through forced-scrolling levels and defended themselves against air targets and ground turrets with bullets and bombs. Enemies dropped power-up capsules which contributed to a power meter, and the player could decide when they wanted to “cash in” those power ups for a ship ability. This mechanic would be repeated in several other games on the NES.
Another central concept that Gradius established was the need to target specific, obvious locations on larger targets or bosses to destroy them. Contra made extensive use of this technique.