Brain Breaker

Brain Breaker is an epic open-world platform-adventure for the Sharp X1 Japanese home computer. It was an early Metroidvania-style game, predating both Metroid and Castlevania. It was designed by Hiroshi Ishikawa and published by Enix in 1985.
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Overview

Brain Breaker is an epic open-world platform-adventure for the Sharp X1 Japanese home computer. It was designed by Hiroshi Ishikawa, who worked on its development since Spring 1984, and published by Enix in 1985. This game is a spiritual successor to Kagirinaki Tatakai, designed by the same creator Hiroshi Ishikawa in 1983. The game was also influenced by Elevator Action.

It was an early Metroidvania-style game, predating Nintendo's Metroid and Konami's Castlevania, which both debuted in 1986. Its Metroidvania style also resembled Xanadu, which released just two months before it.