December 30th of last year, The Arcade Blogger did a piece on the creation of Namco’s classic vertical shooter Xevious.
Xevious was modestly successful in the US, where it was produced by Atari, but it Japan it did amazing numbers. Jeremy Parish (in his NES Works and related series) has mentioned several times that it was a vastly influential game in Japan, inspiring a whole generation of designers, and a whole bunch of clones and similar games. Its US release was around the time of the arcade crash, which was mostly an American thing. If it hadn’t had happened, maybe now we’d think about Xevious the way we consider Pac-Man.
Xevious basically invented the vertical scrolling shooter where your ship has free movement of the screen. It also included a Bomb button to attack objects on the ground, displayed on the game’s background layer. It was a concept that would later be iterated upon in Konami’s Twinbee games.
Revealed in the article is an interesting fact. The scrolling background is stored in ROM as a huge 1024×2048 bitmapped image. That’s much wider than the screen is though. What the game does is send the player into a vertical portion of it 224 pixels wide.
When the player reaches the top, they wrap around to the bottom of another vertical stripe of the game world. In a complete loop, the player will travel from the bottom to the top 16 times. You can tell when you’re about to start another loop because the background will reach a place with trees all the way across!
You always start off a life in a tree-filled area because it begins you at the bottom of a stripe; each vertical pass over the map functions as a checkpoint. The stripes overlap somewhat, so you sometimes pass over an area you’ve seen before but offset by a bit.
For more facts on Xevious and its development, be sure to click through to the article!