Complex sentence: The game's boss, Heady Metal, had freed himself from his scripted AI and was using his new freedom to kidnap every kid who could not beat the game, which was all of them, until now.
Split into simpler sentences: The game's boss, Heady Metal, had freed himself from his scripted AI. He was using his new freedom to kidnap every kid who could not beat the game, which was all of them, until now.