The last invader.

The sound of Space Invaders is four bass notes on a loop. They were composed by Michiyuki Kamei, and at the start of a wave they come slowly, like someone pacing a hallway. As the player shoots, the pace quickens. By the end, with one alien left and crossing the screen at a sprint, the notes have run together into something closer to a pulse. The historian Bill Loguidice compared the effect to a heartbeat, and anyone who has played the game knows the comparison is physical rather than poetic. The game speeds up the player’s body along with the invaders.

What is less often said is that nobody set out to build that acceleration. It began as a symptom. The most imitated feeling in early video games was the side effect of a machine that could not keep up, and the man who noticed it had the nerve to leave it alone.

Tomohiro Nishikado was a designer at Taito, the Japanese amusement company, and he had already made Western Gun, a two-player shootout that Midway sold in America as Gun Fight. His next game began as a response to Atari’s 1976 hit Breakout. He liked the satisfaction of clearing a wall, but he wanted the player to shoot at targets rather than bounce a ball into them. He spent about a year and a half on the project and built custom hardware around an Intel 8080 processor.

The screen he ended up with held 55 invaders in five rows of eleven. They marched sideways, dropped a step at each edge and fired back, while the player sheltered behind four shields that crumbled under fire from both sides. It is a simple picture, and it contained something no arcade game had quite managed before, which was a feeling of siege.

Nishikado’s hardware could not move 55 aliens quickly. It drew each frame of their animation faster when fewer of them were left on the screen, which meant that every invader the player destroyed made the rest move a little faster. The last one crossed the screen at a run. A more fastidious engineer would have smoothed the speed out. Nishikado kept it, and the rising tempo became the emotional shape of the whole game, from calm to panic in a single wave.

The result is a strange moral arrangement. In most contests, doing well makes things easier. In Space Invaders, every success makes the next moment harder, and the player is the one who winds the clock. The better you play, the faster the danger comes, and the only way out is to keep playing well. It is hard to think of a more accurate portrait of ambition in a box that small.

By July 1978 Taito had the game in mass production. Within months, arcades in Japan opened with nothing inside but Space Invaders cabinets, and Taito had installed more than 100,000 machines in Japan by the end of the year. Midway Manufacturing licensed the game for America and brought it out later in 1978.

The craze produced a famous story, that Space Invaders caused a shortage of 100-yen coins in Japan. It is a legend, and it should be told as one. Coin collectors who looked into it found nothing out of the ordinary, the Bank of Japan had no evidence for it, and Nishikado himself has doubted it. The legend survives anyway, perhaps because people needed a story large enough to match the feeling.

The true legacy is smaller and has lasted longer. Space Invaders made the saved high score famous, although it did not invent it; Midway’s Sea Wolf kept a high score in 1976, and let the player reset it. What Nishikado’s game did was make the number the point. Before it, most video games were contests against a clock or against the person standing next to you. After it, the opponent was the machine, and the goal was a figure in the corner of the screen that someone else had put there, often a stranger, often yourself on a better day. A game with a score you could beat alone had no ending, only a target, and players came back day after day to move it.

The game also taught its most devoted players that what looked like chance was arithmetic. A flying saucer crosses the top of the screen from time to time, and its point value seems random. It is not. In the original arcade game, the 23rd shot and every 15th shot after it will score 300 points if it hits the saucer, and since a shot into a shield still counts, a player can use the shields to set up the count. The people who learned this stopped being played by the machine and started playing it, and that distinction is worth more than 300 points.

In 1980 Atari released Space Invaders for the Atari 2600, the first arcade game officially licensed for a home console. It sold more than a million cartridges quickly and about 6 million by 1983, and it quadrupled the console’s sales. For many families it was the reason the 2600 came home at all. The number in the corner came with it, and in the living room it no longer cost a quarter to chase. It cost only time.

Nishikado turned the weakest part of his machine into the strongest part of his game, and the industry has since learned to produce his effect on purpose. The rising tempo, the target that moves just out of reach and the score that invites one more try are now standard equipment, built deliberately into games and into a good deal of software that is not a game at all.

The part that has been imitated least is the ending. The invaders reach the bottom of the screen, or the last one explodes, and the wave is over. The heartbeat stops. The machine that taught a generation to chase a number also, every few minutes, gave it back its evening.