was popularized by Sega's arcade isometric shooter Zaxxon (1981), which Sega followed with the arcade isometric platformer Congo Bongo, released in February 1983. Another early isometric platformer, the ZX Spectrum game Ant Attack, was later released in November 1983. Knight Lore, an isometric sequel to Sabre Wulf, helped to establish the conventions of early isometric platformers. This formula was repeated in later games like Head Over Heels and Monster Max. These games were generally heavily focused on exploring indoor environments, usually a series of small rooms connected by doors, and have distinct adventure and puzzle elements. Japanese developers blended this gameplay style with that of Japanese action-adventure games like The Legend of Zelda to create games like Land Stalker and Light Crusader. This influence later traveled to Europe with Adeline Software's sprawling epic Little Big Adventure, which blended RPG, adventure, and isometric platforming elements. Before consoles were able to display true polygonal 3D graphics, the ¾ isometric perspective was used to move some popular 2D platformers into three-dimensional gameplay. Spot Goes To Hollywood was a sequel to the popular Cool Spot, and Sonic 3D Blast was Sonic's outing into the isometric subgenre. Platform-adventure game Many games fuse platform game fundamentals with elements of action-adventure games, such as The Legend of Zelda, or with elements of RPGs. Typically these elements include the ability to explore an area freely, with access to new areas granted by either gaining new abilities or using inventory items. Many 2D games in the Metroid and Castlevania franchises are among the most popular games of this sort, and so games that take this type of approach are often labeled as "Metroidvania" games. Castlevania: Symphony of the Night popularized this approach in the Castlevania series. Other examples of such games include Hollow Knight, both games in the Ori series (Ori and the Blind Forest and Ori and the Will of the Wisps), Wonder Boy III: The Dragon's Trap, Tails Adventure, Cave Story, Mega Man ZX, Shadow Complex, DuckTales: Remastered. Early examples of free-roaming, side-scrolling, 2D platform-adventures in the vein of "Metroidvania" include Nintendo's Metroid in 1986 and Konami's Castlevania games: Vampire Killer in 1986 and Simon's Quest in 1987, The Goonies II in 1987 again by Konami, as well as Enix's sci-fi Sharp X1 computer game Brain Breaker in 1985, Pony Canyon's Super Pitfall in 1986, System Sacom's Euphory in 1987, Bothtec's The Scheme in 1988, and several