The first game was followed by a heavily modified port for the Family Computer/Nintendo Entertainment System, developed without Kojima's involvement. This game earned enough popularity to garner a sequel, again without Kojima's involvement, released outside Japan. The development of this game inspired Kojima to make an official sequel, Metal Gear 2: Solid Snake. As the series moved into three-dimensional graphics, Kojima decided to title the next game in the series Metal Gear Solid instead of Metal Gear 3; the "Solid" title has been used for all 3D action Metal Gear games since. Several non-action games have also been released, including the Metal Gear Acid games, which have a card-based system of gameplay.