of orange and green cellophane over certain portions of the screen to add color to the image. Later Japanese releases used a rainbow-colored cellophane overlay, and these were eventually followed by versions with a color monitor and an electronically generated color overlay. Music Despite its simplicity, the music to Space Invaders was revolutionary for the gaming industry of the time. Video game scholar Andrew Schartmann identifies three aspects of the music that had a significant impact on the development of game music: Whereas video game music prior to Space Invaders was restricted to the extremities (i.e., a short introductory theme with game-over counterpart), the alien-inspired hit featured continuous musicthe well-known four-note loop, consisting of the first four notes of the descending D minor natural scalethroughout, uninterrupted by sound effects: "It was thus the first time that sound effects and music were superimposed to form a rich sonic landscape. Not only do players receive feedback related directly to their actions through sound effects; they also receive stimulus in a more subtle, non-interactive fashion through music." The music interacts with on-screen animation to influence the emotions of the player: "That seemingly pedestrian four-note loop might stir us in the most primitive of ways, but that it stirs us at all is worthy of note. By demonstrating that game sound could be more than a simple tune to fill the silence, Space Invaders moved video game music closer to the realm of art." The music for Space Invaders popularized the notion of variability—the idea that music can change in accordance with the ongoing on-screen narrative. The variable in Space Invaders, the tempo, is admittedly simple, but its implications are not to be underestimated. "Over the years, analogous strategies of variation would be applied to pitch, rhythm, dynamics, form, and a host of other parameters, all with the goal of accommodating the nonlinear aspect of video games." Next Generation editor Neil West also cited the Space Invaders music as an example of great video game art, commenting on how the simple melody's increasing tempo and synchronization with the enemies' movement chills and excites the player. Reception and versions Arcade version When Nishikado completed the game, it was initially met with a mixed response from within Taito and among amusement arcade owners. His colleagues praised it, applauding his achievement while queuing up to play, whereas his bosses predicted low sales as games often ended more