Short answers, pulled from the story.
An action game is a video game genre that emphasizes physical challenges, particularly hand-eye coordination and reaction time. It encompasses a broad range of subgenres including fighting games, beat 'em ups, shooter games, rhythm games, and platform games. The player typically controls an avatar who must navigate levels, battle enemies, and defeat a boss to advance.
Taito's Space Invaders (1978), designed by Tomohiro Nishikado, is credited with marking the beginning of the golden age of arcade video games. It introduced the concept of going round after round, gave players multiple lives, saved the high score, and featured enemies that could react to the player's movement and fire back.
Shigeru Miyamoto designed Super Mario Bros. (1985) for the Nintendo Entertainment System. He combined the platforming from Donkey Kong and Mario Bros. (1983) with side-scrolling elements from the racing game Excitebike (1984) and the beat 'em up Kung-Fu Master (1984). The game established the conventions of the side-scrolling platformer subgenre.
Irem's Kung-Fu Master (1984) is recognized as the first beat 'em up and the most influential side-scrolling martial arts action game. It was based on two Hong Kong films: Bruce Lee's Game of Death (1973) and Jackie Chan's Wheels on Meals (1984).
Capcom's Street Fighter II (1991) replaced high-score comparison with direct, face-to-face competition between two players. It inspired John Romero to create the deathmatch mode in id Software's Doom (1993), which extended competitive multiplayer into online games.
Scientists at the University of Rochester found that college students who played Unreal Tournament for one month improved their performance in eye examinations by about 20%, compared to those who played Tetris. Separately, researchers from Helsinki School of Economics found that players of the first-person shooter James Bond 007: Nightfire might secretly enjoy having their character killed in the game, even when their expressions suggest otherwise.